KELLOGG  AND 


BY  THE  SAME  AUTHORS 
BY  VERNON  LYMAN  KELLOGG 

ELEMENTARY  ZOOLOGY 

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FIRST  LESSONS  m  ZOOLOGY 

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AMERICAN  INSECTS 

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Edition,  $4.00. 

DARWINISM  TODAY 

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INSECT  STORIES 

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THE  ANIMALS  AND  MAN 

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BY  RENNIE  WILBUR  DOANE 

INSECTS  AND  DISEASE 

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ELEMENTARY  TEXTBOOK  OF 

ECONOMIC  ZOOLOGY 

AND 

ENTOMOLOGY 


SO|l  OF  ENTOMOLOGY   AND   LECTURER  IN  BIONOMICS 
IN  STANFORD   UNIVERSITY 


•AND 


RENNIE  WILBUR  DOANE 


ASSISTANT   PROFESSOR  OF   ECONOMIC  ENTOMOLOGY 
IN  STANFORD   UNIVERSITY 


NEW  YORK 
HENRY  HOLT  AND  COMPANY 


COPYRIGHT,  1915 

BY 
HENRY  HOLT  AND  COMPANY 


THE. MAPLE- PRESS. YORK- PA 


PREFATORY  NOTE 

The  point  of  view  from  which  this  book  is  written  is  explained 
in  its  first  chapter.  For  that  matter  it  is  indicated  clearly  by 
the  title.  If  the  study  of  zoology  is  being  neglected  in  schools 
for  the  alleged  reason  that  it  is  not  a  useful  study,  the  neglect 
is  based  on  an  unsound  reason.  For  zoology  is  useful,  and  not 
in  one  way  alone,  but  in  two  ways;  and  both  of  these  in  addition 
to  its  pedagogic  value  as  a  study  which  develops  accurate  per- 
sonal observation  and  independent  personal  attainment  of 
conclusion. 

Zoology  is  first  of  all  useful  in  the  way  so  often  stressed  by 
Huxley,  as  a  study  that  gives  us  a  sounder  basis  for  our  own 
life  by  showing  the  demands  of  Nature  on  animal  life  in  general 
and  the  kinds  of  responses  to  be  made  to  these  demands.  In 
other  words  it  is  quite  specially  a  branch  of  science  that  can 
help  us  largely  as  a  guide  to  living  in  conformity  to  natural 
laws.  Zoology  is  also  useful  in  a  more  obvious  and  commerci- 
ally ratable  way,  by  revealing  the  precise  relation  which  many 
animals  bear  to  us  in  their  attitude  of  friends  to  be  cultivated, 
or  foes  to  be  fought.  Injurious  insects,  alone,  cause  this 
country  an  annual  loss  of  a  billion  dollars.  A  general  knowl- 
edge of  insect  life  and  an  intelligent  and  vigorous  application 
of  this  knowledge  can  save  the  nation  half  this  loss. 

To  the  teacher  intending  to  use  this  book  as  class  guide  there 
is  due  a  word  of  explanation.  The  authors  have  attempted  to 
make  the  book  an  introduction  to  general  zoology  as  well  as 
to  that  specific  phase  of  it  called  economic.  The  first  chapters 
are  therefore  of  a  nature  to  introduce  pupils  to  general  facts  of 
animal  structure  and  life.  They  are  arranged  on  the  basis  of  ac- 
cepted pedagogic  principles.  The  later  chapters,  arranged  on 
a  basis  of  animal  classification,  proceeding  from  the  simpler  to 
the  more  highly  developed  groups,  include  not  only  general  facts 


2056240 


viii  PREFATORY    NOTE 

pertaining  to  the  groups  treated,  but  introduce  and  give  special 
attention  to  the  economic  relations  of  various  particular  mem- 
bers of  the  groups.  Finally  in  still  later  chapters,  segregated 
in  a  separate  section  of  the  book,  there  is  presented  a  sort  of 
encyclopedic  treatment  of  a  considerable  body  of  facts  wholly 
economic  in  aspect.  These  chapters  are  to  be  used  as  reference 
matter,  collateral  reading,  and  matter  to  suggest  practical 
work,  rather  than  as  material  for  recitation.  Of  the  numerous 
insect  kinds  treated  in  the  chapters  on  injurious  insects,  only  a 
certain  few  will  be  found  in  any  single  region.  Those  few  are 
the  ones  intended  for  study  by  pupils  in  that  region.  The 
study  should  be  mostly  field  work. 

We  wish  to  thank  Professor  Harold  Heath  for  his  kindly 
critical  reading  of  much  of  the  manuscript  of  the  book.  The 
sources  of  such  illustrations  as  are  not  original  with  us  are 
pointed  out  in  the  subscriptions  to  the  figures.  We  owe  thanks 
to  many  friends  in  this  connection. 

V.  L.  K. 
R.  W.  D. 

STANFORD  UNIVERSITY,  CALIFORNIA, 
December,  1914. 


CONTENTS 


PART  I 

CHAPTER  PAGE 

I.     ANIMALS  AND  THE  STUDY  OF  ANIMALS    ....  i 

II.     A  STUDY  OF  THE  FROG 4 

III.  A  STUDY  OF  THE  GRASSHOPPER 14 

IV.  A  STUDY  OF  HYDRA 21 

V.     A  STUDY  OF  AMOEBA 25 

VI.     THE  ONE-CELLED  ANIMALS      .......  29 

VII.     ONE-CELLED  AND  MANY-CELLED  ANIMALS    ...  39 

VIII.     THE  CLASSIFICATION  OF  ANIMALS      .....  48 

IX.     SPONGES  AND  SPONGE  FISHING 58 

X.     SEA-ANEMONES,  JELLY-FISHES,  CORALS  AND  CORAL 

ISLANDS 63 

XI.     LIVER-FLUKES,    TAPE-WORMS,    AND   OTHER   PARA- 
SITIC FLAT-WORMS 69 

XII.     TRICHINAE,    HOOKWORMS,    FILARIA,    AND    OTHER 

PARASITIC  ROUND  WORMS 79 

XIII.  STARFISHES,  SEA-URCHINS,  AND  SEA-CUCUMBERS      .  89 

XIV.  EARTHWORMS,  LEECHES,  AND  OTHER  SEGMENTED 

WORMS " 98 

XV.     CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.      .      .  106 

XVI.     SLIME  SLUGS,  MYRIAPODS  AND  INSECTS  ....  123 
XVII.     CLASSIFICATION  OF  INSECTS,  AND  INSECT  BENEFITS 

AND  INJURIES 153 

XVIII.     INSECTS  (CONT'D)  WASPS,  ANTS,  THE  HONEY  BEE 

AND  OTHER  BEES 183 

XIX.     SCORPIONS,  SPIDERS,  MITES  AND  TICKS  ....  206 
XX.     OYSTERS,  CLAMS,  MUSSELS,  OTHER  MOLLUSCS,  AND 

THE  SHELLFISH  INDUSTRIES         216 

XXI.     FISHES  AND  FISHERIES 237 

XXII.     TOADS,  FROGS  AND  SALAMANDERS 256 

XXIII.  SNAKES,  LIZARDS,  TURTLES,  AND  CROCODILES   .      .  260 

XXIV.  BIRDS.                 273 

XXV.     MAMMALS 295 

ix 


2        ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

are  wholly  wanting  in  inorganic  matter.  Practically  none  of 
the  other  distinctions  usually  given  will  stand  close  scrutiny 
and  critical  analysis. 

A  recent  estimate  by  a  reliable  naturalist  of  the  number  of 
known  kinds  of  animals  puts  this  number  at  522,400.  It  is 
quite  certain  that  there  are  as  many  more  not  yet  known.  Of 
these  million  living  animal  kinds  each  of  us  knows  but  few, 
some  of  us  very  few  indeed.  And  these  few  we  usually  know 
most  superficially;  usually  only  their  general  external  appear- 
ance and  a  little  about  their  habits.  Yet  this  little  that  we 
know  about  animals  is  sufficient  to  serve  as  an  introduction  to 
the  science  of  zoology,  if  we  will  think  seriously  of  it  and  try 
to  arrange  it  in  some  orderly  or  classified  way.  That  indeed 
is  what  the  whole  science  of  zoology  is;  an  orderly  arrangement 
of  all  the  known  facts  about  animals. 

This  arrangement  usually  begins  by  a  grouping  of  the  facts 
under  five  principal  heads.  These  are  animal  classification,  or 
systematic  zoology;  animal  morphology,  or  structural  zoology; 
animal  physiology,  or  functional  zoology;  animal  embryology 
and  life-history,  or  developmental  zoology;  and  animal  rela- 
tions to  their  environment,  or  ecological  zoology.  Animal 
psychology  or  behavior  is  also  sometimes  made  a  special  head 
in  the  classifying  of  zoological  facts,  but  it  may  better  be 
included  in  the  subject  of  animal  physiology. 

No  one  elementary  text-book  can  deal  in  a  comprehensive 
way  with  all  of  these  phases  of  the  study  of  animals.  And  yet 
no  one  phase  can  be  satisfactorily  studied  wholly  by  itself. 
The  classifying  of  animals  into  related  groups  depends  upon  a 
knowledge  of  animal  structure  and  development.  To  under- 
stand animal  structure  one  must  know  something  of  animal 
physiology,  and  vice  versa.  Finally,  to  understand  the  relations 
of  animals  to  the  world  they  live  in,  to  the  plants  that  serve 
them  as  food  and  protection,  to  the  other  animals  that  they 
associate  with  as  friends  or  enemies,  and  to  man,  whose  rela- 
tions with  them  are  much  more  complex  and  important  than 
we  may,  at  first,  think,  it  is  absolutely  necessary  to  know 
something  about  all  the  other  subjects  of  animal  study. 

This  book,  therefore,  which  is  intended  to  guide  students 


ANIMALS,  AND  THE  STUDY  OF  ANIMALS        3 

who  wish  to  learn  about  animals  from  the  special  point  of  view 
of  their  interrelations  with  man,  that  is,  their  possible  use  and 
hurtfulness  and  even  danger  to  us,  and  our  possible  power  to 
develop  this  use  and  minimize  this  injury,  will  be  found  not 
to  neglect  those  other  phases  of  animal  study  which  are  indi- 
cated under  the  titles  of  classification,  morphology,  physiology, 
and  development. 

But  no  text-book  of  zoology  can  really  give  the  student  the 
knowledge  he  seeks.  He  must  find  out  most  of  it  for  himself, 
especially  if  he  wants  it  to  stick.  A  text-book  based  on  the 
experience  of  others  is  chiefly  valuable  for  suggesting  to  him 
how  to  work  most  effectively  to  get  the  knowledge  for  himself. 
And  the  best  students  always  find  out  things  which  are  not  in 
books. 


CHAPTER  II 
A  STUDY  OF  THE  FROG 

Before  beginning  a  discussion  of  the  animal  kingdom  as  a 
whole,  or  of  any  of  the  important  groups  into  which  it  is  divided 
a  few  animals  representing  different  conditions  of  bodily 
make-up  may  be  studied.  The  student  will  then  have  some 
definite,  first-hand  knowledge  of  the  structure  and  organization 
of  animals. 


FIG.  i. — A  common  western  frog,  Rana  boyli. 

A  frog  or  a  common  garden  toad,  may  be  used  as  a  type  of  a 
vertebrate  animal,  that  is,  one  with  a  backbone.  Except 
during  the  cold  winter  months  frogs  may  usually  be  found 
around  ponds  or  along  the  banks  of  streams.  In  the  spring 
and  early  summer  toads,  too,  are  common  around  the  water 
where  they  are  breeding.  Later  in  the  summer  toads  may 
be  found  in  almost  any  garden,  where  they  can  best  be  collected 
at  dusk. 


A  STUDY  OF  THE  FROG  5 

Whenever  possible  the  whole  class  should  join  in  collecting 
the  material  in  order  that  all  may  see  the  animal  in  its  usual 
haunts  and  study  its  habits  there.  Living  specimens  may  be 
kept  in  the  laboratory  for  some  weeks  during  which  time  many 
interesting  observations  may  be  made.  But  in  order  to  make 
a  closer  study  of  the  structure  of  the  animal  it  must  be  killed. 
This  may  be  done  by  placing  the  frog  in  an  air-tight  jar  or  other 
vessel  with  a  piece  of  cotton  or  cloth  that  has  been  saturated 
with  chloroform  or  ether.  The  following  description  is  written 
for  the  frog,  but  it  will  serve  also  as  a  guide  for  the  study  of  the 
toad,  as  the  two  animals  are  alike  in  general  structure. 

External  Structure. — The  body  of  the  frog  is  divided  into 
two  principal  regions,  the  head  and  the  trunk.  In  most  verte- 
brates there  is  a  distinct  neck  between  these  two  regions,  but 
in  the  frog  they  are  closely  united.  The  forelegs,  or  arms, 
are  well  developed,  but  the  hind  legs  are  much  longer  and 
stronger,  enabling  the  animal  to  leap  for  considerable  distances. 
On  the  hands  are  four  fingers  or  digits  and  a  rudiment  of  a 
thumb.  The  five  toes  on  the  hind  legs  are  connected  by  a  web. 

The  tough  skin  that  covers  the  body  is  kept  moist  by  the 
secretions  from  many  glands.  The  eyes  are  large,  prominent 
and  protruding.  When  they  are  closed  they  are  drawn  back 
into  their  orbits  somewhat  and  covered  mostly  by  the  lower 
eyelid,  which  is  thin  and  freely  movable.  The  upper  eyelid  is 
thick  and  not  capable  of  much  movement.  The  tympanum, 
the  outer  membrane  of  the  auditory  organ,  is  a  smooth  ellip- 
tical membrane  just  back  of  each  eye.  When  sound  waves  strike 
the  tympanum,  causing  it  to  vibrate,  the  vibrations  are  trans- 
ferred to  the  inner  ear  by  a  minute  rod,  the  columella,  which 
extends  between  the  two.  The  nostrils  are  in  front  of  the  eyes 
and  above  the  mouth.  The  wide  mouth  extends  from  one 
side  of  the  head  to  the  other.  In  the  frog  there  are  a  few  small 
teeth  on  the  upper  jaw  and  in  the  roof  of  the  mouth  which  serve 
only  to  hold  the  prey.  No  such  teeth  are  present  in  the  toad. 
The  tongue  is  attached  by  its  anterior  end.  The  posterior 
end  is  free  and  can  be  extended  forward  out  of  the  mouth  nearly 
its  full  length  for  capturing  insects.  As  the  tongue  is  covered 
with  a  mucous  secretion  the  insects  stick  to  it  and  are  quickly 


6        ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

drawn  into  the  mouth.  In  the  roof  of  the  mouth  are  two  pairs 
of  openings.  The  anterior  pair,  the  inner  nares,  are  the  in- 
ternal openings  to  the  nose;  the  posterior  pair,  just  posterior 
to  the  eyeballs,  are  the  internal  openings  to  the  wide  Eustachian 
tubes  which  lead  to  the  mouth  from  the  chamber  of  the  ear 
behind  the  tympanum.  At  the  posterior  end  of  the  mouth  is 
the  opening  of  the  esophagus  through  which  the  food  passes 
into  the  stomach.  Just  below  the  opening  of  the  esophagus 
is  a  perpendicular  slit-like  opening,  the  glottis.  This  opens  into 
the  short  larynx  through  which  the  air  passes  to  the  lungs. 
The  flaps  just  within  this  opening  are  the  vocal  cords. 

Internal  Structure. — In  making  the  dissection  for  the  study 
of  the  internal  structure  it  is  best  to  make  the  cut  along  the 
ventral  side  from  the  anal  opening,  at  the  posterior  end  of  the 
body,  to  the  angle  of  the  lower  jaw.  The  first  cut  should  be 
made  only  through  the  skin  in  order  to  expose  some  of  the 
muscles  that  control  the  movements  of  the  body.  The  large 
sheet  of  abdominal  muscles  covering  the  ventral  side  of  the 
frog  consists  of  two  sets,  an  outer  and  an  inner  layer.  Poste- 
riorly they  are  attached  to  the  bony  pelvic  girdle  which  sup- 
ports the  hind  legs.  The  size,  position  and  points  of  attach- 
ment of  the  heavy  bundles  of  muscles  that  control  the  leg 
movements  should  also  be  noted. 

The  incision  may  then  be  made  through  the  body-wall,  and 
the  sides  fastened  back  to  expose  the  internal  organs.  The 
digestive  system  may  be  studied  first.  The  esophagus,  as 
we  have  noted,  leads  from  the  opening  at  the  back  of  the  mouth 
to  the  stomach.  The  stomach  is  somewhat  crescent-shaped, 
and  lies  mostly  on  the  left  side  of  the  body.  The  anterior,  or 
cardiac,  end  is  larger  than  the  posterior,  or  pyloric,  end  where  it 
joins  the  small  intestine.  The  small  intestine  is  a  long  coiled 
tube  opening  into  the  large  intestine  or  rectum.  The  posterior 
part  of  the  rectum  is  known  as  the  cloaca,  for  it  also  receives 
the  waste  products  from  the  bladder  and  kidneys.  The  ova 
and  spermatozoa  also  pass  from  the  body  through  the  cloaca. 
The  reddish-brown  lobes  of  the  liver  are  conspicuous.  They 
secrete  the  bile,  which  is  an  alkaline  fluid  that  aids  in  digestion. 
The  gall-bladder,  where  the  bile  is  stored,  lies  between  the  lobes 


A  STUDY  OF  THE  FROG  7 

of  the  liver  and  opens  into  the  duodenum,  the  first  part  of  the 
small  intestine,  through  the  bile  duct.  The  pinkish,  many- 
lobed  pancreas  lies  between  the  duodenum  and  the  stomach. 
It  also  secretes  a  digestive  fluid  which  is  poured  into  the  duo- 
denum through  the  common  bile  duct.  The  food,  which  con- 
sists chiefly  of  insects  and  worms,  is  first  acted  on  by  the  fluid 
secreted  by  the  mucous  layer  of  tissue  lining  the  esophagus. 
As  it  passes  into  the  stomach  the  acid  gastric  juice  that  is 
secreted  by  the  walls  of  the  stomach  also  acts  upon  it  and 
digests  out  some  of  the  proteid  matter.  In  the  duodenum  the 
bile  and  the  pancreatic  juice  act  upon  the  fats  and  starches. 
The  food,  thus  digested  and  made  available,  is  taken  up  by  the 
•walls  of  the  intestine  and  carried  by  the  blood  and  lymph  to 
all  parts  of  the  body  to  build  up  new  tissue  and  increase  1  he  size 
of  the  body,  or  to  renew  tissue  which  has  been  worn  out  by  the 
various  activities  of  the  animal.  Some  reserve  food  is  stored 
in  the  liver  in  a  form  that  is  available  for  use  when  necessary, 
as  during  the  winter  while  the  frog  is  hibernating.  Nutri- 
ment is  also  stored  in  the  large  many-branched  yellowish  fat 
bodies  which  are  closely  connected  with  the  reproductive  organs. 

The  lungs  are  thin-walled,  sac-like  bodies.  The  area  of  the 
inner  surface  is  increased  by  many  folds  which  form  minute 
spaces,  the  alveoli,  the  walls  of  which  are  abundantly  supplied 
with  blood  capillaries.  The  waste  carbon  dioxide  in  the  blood 
is  given  off  and  the  oxygen  taken  up  through  the  thin  walls  of 
these  capillaries.  The  air  passes  through  the  nostrils  or 
external  nares  into  a  slightly  enlarged  chamber,  the  olfactory 
chamber,  thence  through  the  posteror  nares  into  the  mouth. 
The  nostrils  are  then  closed,  the  floor  of  the  mouth  is  raised,  and 
the  air  is  forced  through  the  glottis  into  the  short  larynx  and 
into  the  lungs.  The  air  is  forced  out  from  the  lungs  by  the 
contraction  of  the  muscles  of  the  body- wall.  While  respiration 
is  carried  on  chiefly  by  the  lungs,  the  skin,  particularly  in  the 
frog,  acts  in  the  same  capacity,  the  transfer  of  gases  taking 
place  through  the  capillaries  there  as  in  the  lungs. 

The  Circulatory  System. — The  blood  of  the  frog  is  a  liquid 
plasma  which  contains  three  kinds  of  corpuscles.  The  com- 
paratively large,  flattened,  elliptical,  red  corpuscles  are  most 


8   ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

numerous  and  give  the  red  color  to  the  blood.  They  contain 
a  substance  called  hemoglobin,  which  takes  up  the  oxygen  in 
the  respiratory  organs  and  carries  it  to  the  other  tissues  of  the 
body.  The  white  corpuscles,  or  leucocytes,  are  amoeboid  in 
character,  and  are  able  to  change  their  shape  and  move  about 
independently.  It  is  their  duty  to  take  up  and  destroy  any 
small  foreign  objects  such  as  bacteria,  parasitic  germs,  bits  of 
broken-down  tissue,  or  other  particles .  that  should  be  elimi- 
nated. In  this  way  they  prevent  the  undue  multiplication  of 
many  disease  germs  that  might  prove  most  serious  if  they 
attained  to  considerable  numbers.  The  spindle-cells  are  cor- 
puscles which  may  later  develop  into  red  corpuscles.  Most 
of  the  blood  corpuscles  are  developed  in  the  marrow  of  the 
bones,  although  many  of  the  white  corpuscles  are  formed  in 
the  spleen,  which  is  a  reddish,  oval  body  lying  above  the  ante- 
rior end  of  the  cloaca.  The  blood  is  contained  in  a  system  of 
veins  and  arteries  with  a  central  pumping  station,  the  heart, 
which  drives  the  blood  out  through  the  blood-vessels  to  all 
parts  of  the  body.  With  the  aid  of  a  microscope  the  blood  may 
plainly  be  seen  circulating  through  the  membrane  between 
a  live  frog's  toes.  Besides  the  red  blood  in  the  closed  circu- 
lation, there  is  a  colorless  lymph  containing  white  corpuscles 
occurring  in  many  lymph  spaces  in  various  parts  of  the  body. 
The  lymph  is  derived  from  the  plasma  of  the  blood  and  ulti- 
mately flows  back  into  the  veins.  The  lymph  spaces  connect 
with  each  other,  and  the  large  lymph  hearts  in  the  dorsal  part 
of  the  body  cavity,  by  their  pulsations,  drive  the  blood  into 
two  of  the  veins  in  the  region  of  the  heart.  ^ 

The  pear-shaped  heart  is  enclosed  in  a  delicate  semi-trans- 
parent sac,  the  pericardium.  It  is  made  up  of  the  conical 
muscular  ventricle  and  the  thinner-walled  right  and  left  auricles. 
When  the  ventricle  contracts,  the  blood  is  driven  out  through 
the  thick-walled  truncus  arteriosus,  which  soon  divides.  Each 
of  the  divisions  gives  off  three  branches,  the  carotid  arteries, 
which  supply  the  head,  the  systemic,  arteries,  which  pass  around 
the  alimentary  canal  and  unite  above  forming  the  dorsal  aorta, 
and  the  pulmonary  arteries,  which  carry  blood  to  the  lungs  and 
the  skin.  The  systemic  arteries  and  the  aorta  give  off  branches 


A  STUDY  OF  THE  FROG  9 

which  carry  blood  to  the  greater  part  of  the  body  and  to  the 
viscera.  The  pulmonary  arteries,  or  pulmo- cutaneous  arteries 
as  they  are  sometimes  called,  divide  just  before  they  reach 
the  lung,  one  branch  passing  out  to  the  skin. 

The  arteries  entering  the  lungs  at  once  divide  into  smaller 
and  smaller  vessels  and  finally  into  the  small  capillaries  where, 
as  already  said,  the  blood  is  purified  by  giving  off  its  carbon 
dioxide  and  taking  up  oxygen.  The  capillaries  collect  again 
into  larger  and  larger  veins  and  the  blood  is  returned  from  the 
lung  to  the  left  auricle  of  the  heart  through  the  pulmonary 
vein.  All  of  the  arteries  that  pass  out  to  the  various  parts  of 
the  body  also  divide  into  smaller  and  smaller  vessels  and  into 
capillaries  which  in  turn  unite  to  form  veins.  Some  of  the 
veins  carry  blood  through  the  kidneys,  where  urea  and  other 
waste  matter  is  taken  out;  others  carry  blood  to  the  liver;  but 
all  of  the  veins  from  the  different  parts  of  the  body  finally 
unite  into  three  large  veins  which  open  into  the  sinus  venosus, 
a  thin-walled  sac  on  the  dorsal  side  of  the  heart.  From  the 
sinus  venosus  the  blood  enters  the  right  auricle.  The  right 
auricle  thus  becomes  filled  with  the  impure  blood,  that  is, 
with  blood  that  has  given  up  its  oxygen  to  the  tissues  in  all 
parts  of  the  body  and  is  carrying  carbon  dioxide  as  waste. 
The  left  auricle,  as  we  have  seen,  is  filled  writh  blood  that  has 
just  returned  from  the  lungs  and  the  skin,  hence  it  is  pure,  that 
is,  it  contains  much  oxygen  and  no  carbon  dioxide.  The  two 
auricles  contract  simultaneously  and  send  the  blood  into  the 
ventricle,  that  from  the  right  auricle  into  the  right  side  of  the 
ventricle,  that  from  the  left  auricle  into  the  left  side.  When 
the  ventricle  contracts  the  impure  blood  in  the  right  side  is 
forced  out  first  and  passes  into  the  pulmonary  arteries,  and  the 
blood  in  the  left  side,  which  has  already  received  its  oxygen, 
is  sent  out  through  the  carotid  and  systemic  arteries,  carrying 
its  oxygen  and  nourishment  to  all  parts  of  the  body.  A 
longitudinal  section  through  the  heart  and  the  beginnings  of 
the  arteries  will  showr  the  valves  that  keep  the  blood  from 
flowing  back  when  the  heart  contracts. 

The  Excretory  System. — The  reddish  glandular  kidneys  lie 
close  to  the  dorsal  body-wall.  They  are  composed  of  connec- 


io      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

tive  tissue  in  which  are  series  of  small  tubules  that  take  out 
much  of  the  waste  material  from  the  blood  that  flows  through 
the  kidneys.  This  waste  material,  urea,  passes  from  the  kid- 
neys through  the  ureters  into  the  cloaca  and  collects  in  the 
sac-like  bladder,  from  which  it  is  finally  expelled  through  the 
anus.  The  skin,  liver  and  the  walls  of  the  intestines  take  some 
part  in  excretion,  but  the  kidneys  are  the  principal  excretory 
organs.  By  the  side  of  the  kidneys  are  the  yellowish  adrenal 
bodies. 

In  the  region  of  the  kidneys  may  be  seen  the  reproductive 
organs.  In  the  female  the  ovaries,  when  filled  with  the  small 
black  and  white  eggs,  are  very  conspicuous.  As  these  eggs 
develop  they  break  out  into  the  body-cavity  and  find  their  way 
into  the  open  ends  of  the  long  convoluted  oviducts.  While 
passing  through  the  oviduct  the  eggs  receive  a  coating  of  an 
albuminous  fluid  which  swells  up  when  it  reaches  the  water. 
The  eggs  are  collected  in  the  posterior  portion  of  the  oviducts 
and  finally  pass  into  the  cloaca  and  out  of  the  body.  The 
white  ovoid  testes  of  the  male  are  attached  to  the  ventral  side 
of  the  kidneys  by  folds  of  the  peritoneum,  which  is  a  membrane 
lining  the  abdominal  wall.  From  each  testis  a  number  of 
delicate  tubes,  called  vasa  deferentia,  enter  the  kidney  and  be- 
come connected  with  the  urinary  tubules.  The  spermatozoa 
that  are  developed  in  the  testes  thus  pass  through  the  kidneys 
and  the  ureters  into  the  cloaca.  The  eggs  are  fertilized  by  the 
spermatozoa  which  is  poured  over  them  while  the  female  is 
laying  them. 

The  Skeleton. — The  bones  making  up  the  skeleton  of  the 
frog  may  be  considered  in  two  groups:  the  axial  skeleton  made 
up  of  the  skull  and  the  vertebral  column,  and  the  appendicular 
skeleton  consisting  of  the  bones  of  the  fore  and  hind  limbs  and 
the  pectoral  and  pelvic  girdles.  The  skull  consists  of  the  bones 
forming  the  immovable  upper  jaw,  the  movable  lower  jaw,  the 
hyoid  apparatus  supporting  the  tongue,  and  a  number  of  bones 
joined  together  to  form  the  narrow  brain  case.  The  vertebral 
column  is  made  up  of  nine  vertebra  followed  by  a  slender  bony 
rod,  the  urostyle.  Each  vertebra  consists  of  lateral  transverse 
processes  and  a  firm  central  portion  which  surrounds  the  neural 


A  STUDY  OF  THE  FROG 


ii 


palatine^ 
fronio-parietal.. 

pterygoid-J.A, 

cervical  vertebra^ 
clavicle — 


splieno-ethnnrid 
maxillary 


digits 


ex-occipital 

supra-scapula 


"-carpels 


radio-ulna 


sacral  vertebra 


'—-calcaneum 


/ 

U  tibio-fibula 

astragalus 
FIG.  3. — Skeleton  of  garden  toad. 


canal.  The  pectoral  girdle,  which  supports  the  fore  limbs 
and  protects  the  organs  in  the  anterior  part  of  the  body,  is 
composed  of  several  bony  or  cartilaginous  pieces.  The  large 
flat  suprascapula  lies  above  the  vertebral  column;  the  scapula, 
clavicle  and  coracoid  pass  downward  on  either  side  and  connect 
with  the  sternal  bones  in  the  median  line.  The  large  humerus 
of  the  arm  is  attached  to  the  pectoral  girdle  between  the  scapula 
and  coracoid.  The  forearm  consists  of  the  fused  radius  and 
ulna,  the  radio-ulna.  The  wrist  contains  six  small  carpal 
bones.  In  the  hand  are  the  five  basal  metacarpal  bones,  and 
beyond  them  the  phalanges,  two  each  in  the  second  and  third 
digits  and  three  in  the  fourth  and  fifth  digits.  The  pelvic 
girdle  is  shaped  somewhat  like  the  "wish-bone"  in  fowls,  the 
long  bone,  the  ilium,  on  each  side  connecting  with  the  trans- 
verse process  of  the  ninth  vertebra.  The  bones  of  the  hind 
limb  consist  of  the  femur,  tibia-fibula,  four  small  tar  sal  bones, 
the  astragalus  and  calcaneum,  the  digital  bones,  consisting  of 
the  metatarsals  and  the  phalanges,  and  the  small  calcar,  or 
prehallux. 

The  Nervous  System. — The  nervous  system  can  best  be 
dissected  out  in  specimens  that  have  been  macerated  in  20  per 
cent,  nitric  acid  for  some  time.  The  brain  consists  of  the  two 
large  fused  olfactory  lobes,  the  elongated  cerebral  hemispheres, 
the  rounded  optic  lobes,  the  small  cerebellum  and  the  long 
medulla  oblongata  which  gradually  narrows  into  the  spinal  cord. 
The  optic  chiasma,  the  infundibulum  and  the  hypophysis  are 
on  the  ventral  side.  The  spinal  cord  extends  through  the 
neural  canal  in  all  the  vertebrae  and  ends  in  the  urostyle.  The 
brain  and  spinal  cord  give  off  many  large  nerves  which  branch 
and  subdivide  and  finally  reach  all  the  tissues  of  the  body.  The 
sympathetic  system  consists  of  two  principal  nerve  trunks,  one 
on  each  side  of  the  vertebral  column,  and  a  series  of  nerves 
which  are  distributed  to  the  internal  organs. 

Life  History  and  Habits. — In  the  spring  the  frog  lays  her 
eggs  in  masses  in  the  water  of  ponds  or  ditches.  The  gelat- 
inous substance  which  surrounds  them  soon  swells  so  that  the 
egg-mass  looks  like  a  ball  made  up  of  little  round  bits  of  jelly 
with  black  centers.  The  toad's  eggs  are  similar  to  the  frog's 


A  STUDY  OF  THE  FROG  13 

eggs,  but  are  laid  in  strings  instead  of  in  masses.  The  young 
tadpoles  which  hatch  from  these  eggs  look  more  like  fish  than 
frogs.  The  body  is  long  and  ends  in  a  long  fin-like,  flattened 
tail.  No  legs  are  present,  and  the  animal  breathes  by  means 
of  two  pairs  of  external  gills.  As  the  tadpoles  grow  and  develop 
first  the  hind  legs  and  then  the  forelegs  begin  to  appear,  lungs 
develop  and  the  gills  disappear,  and  the  tail  shortens  and  finally 
disappears.  The  animal  is  now  frog-like,  though  still  very 
small.  Further  growth  is  very  slow  and  frogs  are  not  really 
adult,  that  is  capable  of  producing  young,  until  they  are  two 
or  three  years  old  or  older. 

The  tadpoles  feed  upon  vegetable  matter  and  minute  ani- 
mals that  they  find  in  the  water.  The  adults  feed  principally 
on  insects  and  worms,  the  toads  especially  destroying  many 
insects  during  the  warm  summer  nights.  As  most  of  these 
insects  are  sure  to  be  injurious  to  some  of  the  garden  crops  the 
toads  are  to  be  regarded  as  great  friends  of  the  horticulturist, 
and  every  effort  should  be  made  to  keep  them  in  the  garden. 
As  a  result  of  a  series  of  studies  on  the  habits  of  the  common 
toad  it  has  been  estimated  that  a  toad  in  a  garden  may  be  worth 
nearly  $20  in  a  single  season.  As  they  may  live  for  ten  years 
or  longer  they  are  truly  valuable  assets  of  the  gardener. 

Toads  and  frogs  have  many  enemies,  among  the  most  im- 
portant of  which  are  snakes  and  some  of  the  shore  birds.  From 
some  of  these  enemies  they  have  little  or  no  protection  save 
their  nocturnal  habits  and  their  ability  to  dive  deep  into  the 
water  when  alarmed.  The  milky  fluid  which  is  secreted  by 
ertain  glands  in  the  skin  protects  them  from  some  animals  which 
might  otherwise  be  important  enemies.  There  is  no  founda- 
tion for  the  belief  that  the  toad  will  cause  warts  to  appear  on 
the  hands  of  a  person  handling  it,  nor  for  many  of  the  other 
curious  superstitions  concerning  this  perfectly  harmless  little 
animal. 


CHAPTER  III 
A  STUDY  OF  THE  GRASSHOPPER 

As  grasshoppers,  or  locusts,  are  among  our  most  common 
animals,  one  of  these  may  be  taken  as  a  representative  of  the 
great  group  of  invertebrates,  or  animals  without  a  backbone. 

When  collecting  specimens  for  this  study  both  winged  and 
wingless,  or  apparently  wingless,  individuals  may  be  found. 
This  depends  on  the  fact  that  when  young  grasshoppers  issue 
from  the  eggs  they  look  much  like  the  adults,  but  are  without 


FIG.  4. — Three  different  stages  of  a  locust,  Melanoplus  fcmur-rubrum; 
a,  just  hatched,  without  wing-pads;  b,  a  later  stage  showing  wings  begin- 
ning to  develop;  c,  adult,  with  fully  developed  wings. 

wings,  and  the  head  and  hind  legs  are  often  abnormally  large. 
As  the  insects  pass  through  the  successive  stages  of  growth, 
rudimentary  wings  appear.  These  increase  in  size  from  time 
to  time  until  the  adult  condition  is  reached. 

Division  of  the  Body  into  Regions. — The  body  is  divided 
into  three  well-defined  regions,  the  head  with  its  eyes,  antenna 
(feelers)  and  mouth-parts,  the  thorax,  which  bears  the  two  pairs 
of  wings  and  the  three  pairs  of  legs,  and  the  abdomen,  which 

14 


A  STUDY  OF  THE  GRASSHOPPER 


is  composed  of  a  series  of  more  or  less  similar  body  rings  or 
segments. 

The  Body-wall. — Some  parts  of  the  skin  or  outer  body- 
wall  are  quite  firm  and  horny  in  texture,  others  are  more 
parchment-like,  and  there  are  still  other  places  in  it,  such  as  the 
neck  and  between  the  segments  of  the  legs  and  the  segments 
of  the  abdomen,  where  the  skin  is  soft  and  flexible.  These 
differences  are  due  to  the  fact  that  a  horny  substance  called 
chitin  is  abundantly  deposited  in  parts  of  the  skin  thus 

antennas 


auditory  organ 
ocellus  I 

•!  head  Compound  eye  / 


—ovipositor 


femur> 
tibia''' 

tarsal  segments 

FIG.  5. — The  red-legged  locust,  Melanoplus  femur-rubrum,  to  show  exter- 
nal structure. 

making  it  firm  for  the  protection  of  the  internal  organs,  and 
for  the  attachment  of  muscles.  Wherever  motion  or  the  bend- 
ing of  the  body-wall  is  desirable,  little  or  no  chitin  is  deposited. 
The  chitinized  portions  of  a  segment  are  called  sclerites.  The 
furrows  or  lines  between  the  sclerites  are  called  sutures. 

The  Head. — Although  the  head  is  apparently  a  single  seg- 
ment, it  is  really  composed  of  several  body  segments  greatly 
modified  and  firmly  fused  together,  making  a  strong  box  which 
contains  what  may,  by  analogy,  be  called  the  brain,  and  certain 
other  important  organs.  On  each  side  of  the  head  are  the  large 


16      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

conspicuous  compound  eyes.  These  eyes  are  called  compound 
because  they  are  made  up  of  a  great  number  of  small  eyes  lying 
very  close  together.  Examined  with  a  hand  lens  or  the  low 
power  of  a  microscope  the  compound  eyes  show  a  honeycomb- 
like  structure,  each  of  the  small  hexagonal  facets  being  the 
external  surface  of  a  simple  eye.  In  slight  depressions  just  in 
front  of  the  eyes  are  the  bases  of  the  long,  many-segmented 
antenna.  These  antennae  are  sense  organs  and  are  used  by 
the  locust  for  feeling  and  perhaps  also  for  smelling.  In  many 
other  insects  they  are  modified  and  plainly  used  for  smelling 
and  also,  in  some,  for  hearing.  In  the  middle  of  the  front  of 
the  head,  a  little  lower  than  the  bases  of  the  antenna?,  is  a  small 
transparent  hemispherical  simple  eye  or  ocellus.  Just  above 
the  bases  of  the  antennas  and  close  to  the  compound  eyes  are 
two  other  simple  eyes.  The  structure  and  function  of  these 
three  ocelli  as  well  as  the  structure  of  the  compound  eye  is 
discussed  in  Chapter  XVI.  On  the  lower  side  of  the  head  are 
the  mouth-parts.  The  upper,  broad,  flap-like  piece,  the 
labrum,  covers  a  pair  of  black  or  brown,  strongly  chitinized, 
toothed  jaws,  or  mandibles.  Back  of  the  mandibles  is  a  second 
pair  of  jaw-like  structures,  the  maxilla,  each  of  which  is 
composed  of  several  parts,  and  back  of  the  maxillae  is  the  labium 
which  is  also  composed  of  several  pieces.  Each  maxilla 
bears  a  slender  feeler,  or  palpus,  composed  of  five  segments. 
The  labium  bears  a  pair  of  similar  palpi,  which  are,  however, 
only  three-segmented.  The  mandibles  and  maxillae,  which  are 
the  insect's  jaws,  move  laterally,  not  vertically,  as  with  most 
animals.  They  are  well  adapted  for  tearing  and  crushing  the 
leaves  or  other  plant  tissue  upon  which  the  locust  feeds.  Some 
other  kinds  of  insects  will  be  found  to  have  these  mouth-parts 
curiously  modified,  enabling  them  to  pierce  the  animal  or 
vegetable  tissues  on  which  they  are  feeding  or  to  lap  up  or 
suck  up  liquid  substances. 

The  Thorax. — The  thorax  is  composed  of  three  segments 
which  can  be  easily  recognized  by  the  appendages  which  they 
bear.  The  first  segment,  the  prothorax,  is  freely  movable  and 
is  covered  by  a  large  hood-shaped  piece,  the  pronotum,  which 
also  extends  back  over  the  next  segment.  The  first  pair  of 


A  STUDY  OF  THE  GRASSHOPPER  17 

legs  is  attached  to  this  segment.  Between  the  forelegs  there 
is,  on  many  species  of  grasshoppers,  a  short,  blunt  tubercle. 
The  second  and  third  segments,  the  mesothorax  and  the 
metathorax,  are  immovably  fused,  but  their  borders  are  indicated 
by  well-marked  sutures.  There  is  also  on  the  side  of  each 
segment  a  suture  near  the  middle  which  divides  the  sides  of  the 
segments  into  two  sclerites.  The  mesothorax  bears  the  second 
pair  of  legs,  which  are  similar  to  the  first  pair,  and  the  first 
pair  of  wings.  The  metathorax  bears  the  large,  third  pair  of 
legs  and  the  second  pair  of  wings. 

Each  leg  is  composed  of  several  successive  parts  or  segments. 
The  segment  nearest  the  body  is  sub-globular  and  is  called  the 
coxa;  the  second  segment  is  smaller  than  the  coxa  and  is  called 
the  trochanter;  the  third,  the  largest,  is  the  femur;  the  fourth, 
the  tibia,  is  long  and  slender;  the  three  short  segments  beyond 
the  tibia  are  called  the  tar  sal  segments.  The  terminal  segment, 
which  is  longer  and  more  slender  than  the  others,  bears  a  pair 
of  claws,  between  which  is  a  little  pad,  the  pulmllus.  The 
tibiae  are  armed  with  small  spines,  and  the  femora  of  the  last 
pair  of  legs  are  enormously  developed,  enabling  the  insect  to 
leap  some  distance.  Just  above  the  base  of  each  of  the  middle 
pair  of  legs  is  a  small,  slit-like  opening,  or  spiracle,  guarded  by 
two  fleshy  lips.  These  spiracles  are  the  external  openings  of  a 
set  of  fine  tubes  forming  the  respiratory  system,  which  as  we 
shall  see,  carries  air  to  all  parts  of  the  body. 

The  front  wings  are  long,  narrow  and  parchment-like,  with 
branched  and  unbranched  longitudinal  veins  and  many  short 
cross-veins.  The  hind  wings  are  triangular  in  outline,  mem- 
branous, and  when  at  rest  are  folded  like  a  fan.  Some  of  the 
veins  at  the  base  of  each  pair  of  wings  are  thickened  and  raised 
or  depressed  in  such  a  way  that  they  set  the  wings  to  vibrating 
rapidly  when  they  are  rubbed  together.  This  produces  the 
crackling  sound  sometimes  heard  when  grasshoppers  are  flying. 
A  somewhat  similar  sound  is  produced  when  the  insect,  at 
rest,  rubs  the  roughened  inner  surface  of  the  hind  femora 
against  the  outer  pair  of  wings. 

Abdomen. — The  first  segment  of  the  abdomen  has  its  upper, 
or  dorsal,  and  lower,  or  ventral,  parts  widely  separated  by  the 


1 8      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

cavities  for  the  insertion  of  the  hindmost  legs.  The  ventral 
part  of  this  segment  is  dovetailed  into  the  ventral  part 
of  the  metathorax  and  appears  to  be  a  part  of  it.  In  the 
lower  angle  of  the  dorsal  part  there  is  on  each  side  a 
large  opening,  the  external  opening  of  the  auditory 
organ.  The  thin  membranes  within  these  openings  are 
the  tympana.  The  crickets  and  katydids  have  similar 
auditory  organs  situated  in  the  tibiae  of  the  front  legs.  Most 
other  insects  are  believed  to  have  the  sense  of  hearing 
situated  in  the  antennae.  The  second  to  the  eighth  abdominal 
segments  are  ring-like  and  similar.  Close  to  the  anterior  mar- 
gin of  each  segment  just  above  the  lateral  line  is  a  small  spiracle 
similar  to  the  one  on  the  mesothorax  but  much  smaller.  The 
first  abdominal  spiracles  are  on  the  first  segment  just  in  front 
of  the  auditory  organs.  The  terminal  segments  of  the  abdo- 
men are  different  in  the  male  and  female.  The  female  has  at 
the  tip  of  its  abdomen  two  pairs  of  strong,  curved,  pointed 
pieces  which  compose  the  ovipositor,  or  egg-laying  organ.  By 
alternately  bringing  together  and  separating  the  two  pairs  of 
processes  that  form  the  ovipositor  and  at  the  same  time  push- 
ing the  abdomen  into  the  ground  the  female  is  able  to  make  a 
deep  hole  in  which  she  deposits  her  eggs.  The  end  of  the 
abdomen  of  the  male  is  rounded  and  has  three  short  incon- 
spicuous pieces  on  the  dorsal  surface. 

INTERNAL  ANATOMY 

By  carefully  cutting  away  one  side  of  the  body-wall  most  of 
the  internal  organs  will  be  exposed.  The  alimentary  canal 
occupies  the  greater  part  of  the  body-cavity.  Its  different 
divisions,  such  as  the  short  esophagus  leading  from  the  mouth  to 
the  much  enlarged  crop  which  extends  through  the  thorax  to 
the  stomach,  may  be  easily  distinguished.  The  stomach 
extends  to  about  the  seventh  segment  of  the  abdomen  and 
ends  in  the  large  intestine.  The  small  intestine  is  a  short  tube 
running  from  the  end  of  the  large  intestine  to  the  anal  opening 
at  the  end  of  the  body.  The  gastric  caca  are  a  series  of  pouch- 
like  organs  which  open  at  the  union  of  the  crop  and  the  stom- 


A  STUDY  OF  THE  GRASSHOPPER  19 

ach.  They  secrete  a  fluid  which  aids  in  digestion.  The 
Malpighian  tubules  are  a  number  of  fine  hair-like  tubes  which 
arise  from  the  alimentary  canal  at  the  point  of  union  of  the 
stomach  and  the  large  intestine.  They  gather  from  the  blood 
and  empty  into  the  intestine  certain  waste  products,  thus 
functioning  something  like  the  kidneys  of  higher  animals. 

The  muscular  system  comprises  many  sets  of  muscles,  the 
largest  and  strongest  of  which  are  in  the  thorax.  As  there  is 
no  internal  skeleton  the  muscles  are  attached  to  the  hardened 
portions  of  the  body-wall. 

The  respiratory  system  consists  of  series  of  small  many- 
branching  tubes  called  trachea.  Their  walls  are  thin  and  elastic. 
The  external  openings  of  these,  the  spiracles,  have  already 
been  noted.  From  the  spiracles  short  tubes  lead  to  two  lateral 
trunks  which  send  off  branches  to  a  pair  of  dorsal  trunks. 
These  lateral  and  dorsal  trunks  send  branches  to  all  the 
organs  and  tissues  of  the  body.  The  air  enters  the  tracheae 
through  the  spiracles  and  is  carried  to  all  parts  of  the  body, 
where  oxygen  is  given  up  to  the  tissues  which  need  it,  and  the 
waste  carbon  dioxide  is  carried  away. 

The  reproductive  system  of  the  female  is  easily  dis- 
tinguished if  the  female  has  been  collected  in  the  fall  or  late 
summer  before  she  has  laid  her  eggs.  At  such  a  time  almost 
the  whole  abdomen  will  be  filled  by  the  pair  of  thin-walled 
ovaries  in  which  may  be  seen  the  masses  of  oblong,  brownish 
or  yellowish  eggs.  Running  from  the  posterior  end  of  each 
ovary  is  a  small  tube,  the  oviduct.  These  unite  near  the  pos- 
terior end  of  the  body  and  form  a  single  tube  which  opens 
between  the  bases  of  the  valves  of  the  ovipositor.  The  repro- 
ductive organs  of  the  male  are  similar  to  those  of  the  female 
but  much  smaller.  They  consist  of  a  pair  of  testes  which  lie 
on  the  dorsal  side  of  the  posterior  part  of  the  stomach.  Lead- 
ing from  the  testes  are  two  very  small  tubes,  the  vasa  deferentia, 
which  unite  to  form  a  short  tube  that  opens  on  the  dorsal 
surface  of  the  last  segment  of  the  abdomen.  These  organs 
cannot  be  easily  distinguished  unless  the  specimen  is  in  just 
the  right  condition. 

The  nervous  system  is  made  up  principally  of  a  series  of 


20      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

ganglia,  small  masses  of  nerve  cells  and  tissue,  which  are  con- 
nected with  each  other  by  a  pair  of  white  nerve  cords.  The 
largest  of  these  ganglia  is  situated  in  the  head  above  the  esoph- 
agus and  is  called  the  brain.  Nerve  cords  which  unite  this 
ganglion  with  one  below  the  esophagus  pass  on  either  side  of 
the  esophagus.  From  this  ganglion  a  pair  of  longitudinal  cords, 
very  close  together,  pass  backward  along  the  floor  of  the  body. 
At  intervals  along  these  cords  are  ganglia  from  which  fine 
branching  nerve  fibers  run  to  all  parts  of  the  body. 

The  circulatory  system  consists  of  an  elongate,  thin-walled 
dorsal  vessel  called  the  heart  situated  just  under  the  dorsal 
wall  of  the  abdomen.  It  is  not  easily  distinguished  except  in 
fresh  specimens.  Its  structure  will  be  described  in  a  later 
chapter  where  the  internal  anatomy  of  a  caterpillar  is  discussed. 
(See  Chapter  XVI.)  There  are  no  arteries  or  veins.  The 
colorless  blood  of  the  insect  fills  all  the  space  of  the  body-cavity 
not  occupied  by  organs  and  other  tissues,  and  is  in  an  enclosed 
vessel  only  while  passing  through  the  heart. 


CHAPTER  IV 
A  STUDY  OF  HYDRA 

Frogs  and  grasshoppers  and  all  the  other  vertebrates  and 
insects  are  very  complex  animals,  having  their  bodies  made  up 
of  many  highly  specialized  organs  and  tissues,  each  part 
adapted  to  performing  some  special  life  process.  There  are 
other  many-celled  animals  much  simpler  in  structure  than 
this,  animals  without  specially  developed  digestive,  nervous, 
muscular  or  reproductive  systems.  Yet  they  are  capable  of 
doing  all  of  the  essential  things  that  the  more  complex  animals 
can  do.  They  can  take  and  assimilate  food,  respond  to  stimuli, 
move,  and  reproduce  their  kind.  Hydra  is  a  good  example 
of  such  a  simple  animal,  and  as  it  is  to  be  found  in  most  open 
fresh- water  ponds,  in  water  troughs  and  other  places  where  the 
water  is  not  too  stagnant,  it  may  be  taken  as  a  type  for  study. 

Hydrae  will  often  be  found  attached  to  a  stone,  stick  or  leaf, 
or  to  the  green,  moss-like  plants  that  are  often  found  in  stand- 
ing water.  They  may  be  green  or  brownish  in  color  and  as 
they  are  only  about  one-eighth  of  an  inch  long  or  even  smaller, 
they  will  have  to  be  looked  for  very  carefully.  Once  seen, 
however,  they  may  be  easily  recognized  by  the  cylindrical  body 
attached  by  the  base  and  with  its  free  end  crowned  with  a 
circlet  of  slender  tentacles  or  arms  which  lash  about  slowly 
while  the  animal  is  extended.  When  touched  or  alarmed  the 
whole  body  is  quickly  contracted  and  the  tentacles  drawn  in, 
so  that  the  animal  now  looks  like  a  simple,  small,  round  or  oval 
projection  on  the  leaf  or  stone.  Food  is  caught  by  the  ten- 
tacles and  conveyed  to  the  mouth,  which  lies  in  the  center  at 
the  base  of  the  tentacles.  Through  the  mouth  the  food  passes 
into  a  space,  the  digestive  cavity,  surrounded  only  by  the  body- 
wall.  The  food  is  dissolved  in  this  cavity  and  the  waste  parts 


22      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

thrown  out  through  the  mouth  opening.     The  digestive  cavity 
extends  out  into  the  tentacles. 

In  a  prepared  cross-section,  the  body  of  Hydra  is  seen  to 
be  a  hollow  cylinder  with  walls  made  up  of  two  well-defined 
layers  of  cells  with  a  thin  non-cellular  layer  between  them. 
Some  of  the  cells  of  the  outer  layer,  or  ectoderm,  have  contractile 
basal  processes  running  parallel  to  the  long  axis  of  the  body. 


FIG.  6. — Hydra.   Note  two  tentacles  catching  an  insect  larva;  note  the 
budding  young  Hydra.     (Natural  size,  one-sixth  inch;  from  life). 

Like  the  muscle  cells  of  higher  animals  these  cells  contract 
under  certain  stimuli,  and  the  whole  body  of  the  animal  is 
shortened,  as  we  have  seen.  Among  these  cells,  particularly 
on  the  upper  part  of  the  body  and  on  the  tentacles,  are  small 
stinging  cells  called  nematocysts.  The  cells  within  which  nema- 
tocysts  develop  are  called  cnidoblasts,  and  each  is  provided  at 


A  STUDY  OF  HYDRA  23 

its  outer  end  with  a  trigger-like  process,  the  cnidocil.  The 
long  thread-like  tubes  that  are  shot  out  when  the  nematocysts 
are  exploded  carry  a  poison  called  hypnotoxin,  which  paralyzes 
or  kills  minute  animals  that  are  stung  by  them. 

The  endoderm  lines  the  digestive  cavity.  Some  of  the  endo- 
derm cells  are  provided  with  fine  threads,  or  flagella,  whose 
lashings  set  up  currents  that  waft  the  food  in  and  out.  Other 
cells  are  furnished  with  blunt  processes  which  may  surround 
and  engulf  some  of  the  food  particles,  and  digest  them. 


ovy 


FIG.  7. — Diagram  of  a  longitudinal  section  of  Hydra,  bd,  buds,  the 
upper  one  just  beginning  to  develop;  ect,  ectoderm;  end,  endoderm;  hyp, 
hypostome;  mth,  mouth;  net,  nematocysts;  ovy,  ovary;  spy,  spermary. 
(After  Parker  and  Haswell.) 

Some  of  the  endoderm  cells  have  contractile  processes  like 
those  of  the  ectoderm.  The  middle,  non-cellular  layer  is  a 
thin  homogeneous  layer  on  each  side  of  which  lie  the  con- 
tractile roots  of  the  cells  of  the  ectoderm  and  endoderm. 

Hydra  may  produce  new  individuals  either  asexually  or 
sexually.  In  some  individuals  small  swellings  or  buds  may  be 
observed,  usually  near  the  base.  At  first  these  are  simply 
evaginations  of  the  body-wall,  but  later  they  develop  tentacles 


24      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  a  mouth  of  their  own.  Finally  the  buds  become  constricted 
at  the  base  and  separate  from  the  parent.  The  young  Hydras 
thus  produced  soon  attach  themselves  to  some  object  and  begin 
their  independent  existence.  This  budding  takes  place  more 
commonly  when  food  is  plentiful  and  other  conditions  are 
favorable.  At  other  times  reproductive  organs,  ovaries  and 
spermaries,  may  be  formed,  and  the  animal  produces  special 
germ  cells.  The  ovaries  appear  as  thickenings  of  the  body- 
wall  near  the  lower  end  of  the  body.  In  each  ovary  a  single 
ovum  or  egg  develops.  The  spermaries  appear  as  smaller 
thickenings  of  the  ectoderm  near  the  tentacles.  In  them  the 
sperm  cells  develop.  When  these  reproductive  elements  are 
ripe  they  are  cast  out  into  the  water  where  the  ova  are  ferti- 
lized by  the  spermatozoa.  Thus  Hydra  is  hermaphroditic, 
that  is,  both  sexes  are  represented  in  a  single  individual. 
We  will  find  that  many  worms,  snails  and  some  other  ani- 
mals are  also  hermaphroditic.  In  such  animals  various 
methods  are  adopted  to  prevent  self-fertilization.  In  Hydra 
this  is  prevented  by  the  ova  and  spermatozoa  in  any  indi- 
vidual usually  ripening  and  being  cast  into  the  water  at  dif- 
ferent times.  The  fertilized  ovum  soon  divides  into  a  large 
number  of  cells,  forming  the  embryo,  and  after  becoming 
surrounded  by  a  hard  shell  or  cyst  drops  to  the  bottom  of 
the  pond  where  it  may  remain  for  some  time  before  it  goes 
on  with  its  development. 

Sometimes,  through  accident,  a  Hydra  may  be  cut  into  two 
or  more  pieces.  Each  part  has  the  power  of  developing  into 
a  new  individual  Hydra  just  like  the  original.  This  power  of 
developing  anew  parts  of  the  body  that  may  have  been  lost, 
is  possessed  by  many  other  animals,  especially  the  lower  ones, 
and  is  known  as  regeneration. 


CHAPTER  V 
A  STUDY  OF  AMCEBA 

The  animals  that  we  know  best  are  all  comparatively  large 
and  have  a  body  composed  of  many  cells.  Ordinarily  we  think 
of  a  mouse  or  a  humming-bird  as  being  very  small,  but  in  the 
insect  world  there  are  hosts  of  animals  so  small  that  they  can 
hardly  be  detected  without  the  use  of  a  magnifying  lens.  Yet 
even  the  smallest  of  them  are  as  giants  when  compared  with 
any  of  the  one-celled  animals,  the  Protozoa  (Gr.  protos,  first; 
zoon,  animal),  very  few  of  which  can  be  seen  with  the  unaided 
eye.  Before  the  invention  of  the  microscope  the  Protozoa 
belonged  to  an  unseen  and  unknown  world.  The  earliest 
lenses  enabled  the  observers  to  see  some  of  the  largest  of 
them,  and  each  improvement  of  the  microscope  has  enabled 
us  to  penetrate  further  and  further  into  this  fascinating  field. 
Now  we  know  in  detail  the  structure  and  life  history  of  many 
of  these  almost  inconceivably  minute  animals. 

Most  of  the  Protozoa  live  in  water,  but  a  few  live  in  damp 
sand  or  moss,  while  many  live  in  the  bodies  of  other  animals 
where  they  may  or  may  not  cause  serious  injury.  No  moun- 
tain stream  is  too  pure,  no  ditch  too  foul  to  be  the  home  of  some 
of  these  simple  animals. 

Amoeba. — Among  the  most  familiar  of  these  one-celled  ani- 
mals are  the  Amoebae.  They  are  most  easily  found  in  pools  of 
water,  either  in  the  slime  or  ooze  on  the  bottom  or  in  the 
sediment  that  has  settled  on  submerged  leaves  or  sticks.  If 
some  of  this  material  is  collected  and  poured  into  a  dish  of  water 
and  allowed  to  settle  for  a  few  hours,  Amoebae  may  usually  be 
found  when  small  drops  of  the  slime  are  examined  on  a  slide 
under  the  microscope.  With  the  low-power  lenses  they 
appear  as  small,  semi-transparent,  irregular-shaped  objects 
which,  if  watched  carefully,  will  be  seen  to  move  very  slowly. 

25 


26      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Using  the  higher  power  lenses  it  will  be  seen  that  the  outer  part 
of  the  jelly-like  body,  called  ectosarc,  is  clearer  than  the  more 
granular  inner  part,  the  endosarc,  and  that  within  the  endosarc 
are  many  small  granules,  the  food  particles,  and  a  compara- 
tively large,  round,  clear  space,  the  contractile  vacuole,  which 


FIG.  8. — Amceba  sp.     Showing  the  forms  assumed  by  single  individual  in 
four  successive  changes.     (Greatly  magnified;   from  life.) 

appears  and  disappears  with  more  or  less  regularity.  Some- 
times the  darker,  denser  nucleus  can  be  seen  in  .the  living 
Amoebae,  but  it  shows  much  more  distinctly  in  specimens 
killed  by  allowing  a  little  carmine  or  other  staining  fluid  to 
run  under  the  cover-glass. 

Active  Amoebae  are  constantly  changing  their  shape,  and  by 


A  STUDY  OF  AMCEBA  27 

these  changes  they  effect  a  slow,  flowing  movement.  Small 
unequal  projections,  called  pseudopodia,  stretch  out  from  various 
parts  of  the  body.  At  first  these  are  formed  only  by  the 
ectosarc,  but  as  they  grow  longer  and  larger  the  endosarc  flows 
out  into  some  while  others  are  withdrawn  and  new  ones  are 
thrown  out.  The  outline  of  the  body  thus  continually  changes. 
As  the  animals  move  slowly  about  they  come  in  contact  with 
other  minute  animals  or  plants  around  which  the  pseudopodia 
flow  and  these  organisms,  which  the  Amceba  uses  for  food, 
are  thus  taken  directly  into  the  body.  Any  particles  of  food 
or  other  substances  which  are  taken  into  the  body  and  not 
digested  pass  out  just  as  they  entered,  that  is,  the  Amceba 
flows  away  and  leaves  them,  much  as  a  drop  of  oil  that  sur- 
rounded a  particle  of  sand  might  flow  away  and  leave  the 
sand. 

The  oxygen  that  the  Amoebae  need  is  absorbed  from  the 
surrounding  water.  Some  of  the  waste  excretions  of  the  body 
are  absorbed  directly  by  the  water,  others  are  forced  out  by 
the  contractile  vacuole. 

Thus  we  see  that  while  the  Amceba  has  no  mouth  or  ali- 
mentary canal,  no  lungs  or  heart,  muscles,  glands  or  any  of  the 
special  organs  and  tissues  that  go  to  make  up  the  higher  ani- 
mals; this  minute  speck  of  living  substance  moves,  feeds, 
respires,  excretes  and  does  all  the  essential  things  that  the  more 
complex  organisms  do.  As  the  Amceba  feeds  it  grows  until 
it  reaches  a  more  or  less  definite  size,  then  certain  changes 
take  place  in  the  nucleus  which  soon  divides  into  two  equal 
portions,  one  portion  withdrawing  to  one  part  of  the  body  and 
the  other  part  to  the  opposite  end.  Then  the  substance 
around  the  nuclei  begins  to  divide,  a  portion  collecting  around 
each  of  these  nuclei.  Finally  the  two  halves  pull  entirely 
away  from  each  other  and  thus  two  new  Amoebae  are  formed, 
each  like  the  original,  but  only  half  as  large. 

Amoebae  continue  to  live  and  multiply  as  long  as  the  condi- 
tions surrounding  them  are  favorable.  But  when  the  pond 
dries  up  the  Amoebae  in  it  would  be  exterminated  were  it  not 
for  a  careful  provision  of  nature.  When  the  pond  begins  to 
dry  up  each  Amoeba  contracts  its  pseudopodia  and  secretes 


28      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

a  horny  capsule  about  itself.  It  is  now  protected  from  dry 
weather  and  can  be  blown  by  the  winds  from  place  to  place. 
If  it  again  reaches  water  it  expands,  throws  off  the  capsule 
and  commences  active  life  again  in  the  new  pond. 


CHAPTER   VI 
ONE-CELLED  ANIMALS    (BRANCH  PROTOZOA) 

The  Amoeba  which  has  just  been  studied  is  one  of  the  sim- 
plest of  the  one-celled  animals.  Others  while  still  retaining 
the  one-celled  condition,  become  more  highly  specialized  along 
certain  lines  and  show  a  wonderful  power  to  adapt  themselves 
both  in  form  and  habits  to  the  various  conditions  under  which 
they  live.  A  brief  study  of  a  few  of  these  will  be  worth  while. 

Paramoecium. — Paramcecia  are  usually  found  in  considerable 
numbers  in  any  pond  of  stagnant  water.  A  good  supply  can 
often  be  obtained  by  placing  sticks  or  leaves  from  a  pond, 
together  with  some  dry  hay  or  clover,  in  a  dish,  which  is  then 
filled  with  water  and  allowed  to  stand  for  several  days.  When 
very  abundant  the  Paramoecia  may  even  be  seen  with  the 
unaided  eye  as  minute  white  specks  near  the  edge  of  the  dish. 
Examined  with  the  low  power  of  the  microscope  they  will  be 
seen  as  very  active,  slipper-shaped  animals  much  larger  than 
the  Amoebae.  As  they  move  about  so  rapidly  it  is  desirable 
to  put  them  into  some  thicker  medium,  such  as  a  thin  mixture 
of  cherry  gum;  or  a  few  shreds  of  cotton  may  be  put  under 
the  cover-glass  and  some  of  the  Paramcecia  will  become  en- 
tangled in  this  in  such  a  way  that  they  may  be  studied. 

It  will  at  once  be  seen  that  Paramoecium  differs  from  Amoeba 
in  many  respects.  It  has  a  definite  and  persistent  elongate- 
oval  shape,  roughly  like  that  of  a  slipper,  hence  it  is  often 
called  the  slipper  animalcule.  There  are  definite  anterior 
and  posterior  ends  and  dorsal  and  ventral  sides,  and  the  body  is 
covered  with  minute  cilia,  fine  hair-like  projections,  which 
vibrate  very  rapidly  and  propel  the  animal  through  the  water. 
On  one  side,  beginning  at  the  anterior  end  and  extending  more 
than  half  the  length  of  the  animal,  is  a  buccal  groove,  which  is 
provided  with  many  small  cilia  which  drive  water  currents  and 

29 


30      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


all  kinds  of  particles  into  the  gullet  which  opens  into  the  inte- 
rior. Food  particles  surrounded  by  a  film  of  water  are  taken 
into  the  body  through  this  opening  and  are  digested  just  as 
they  are  in  the  body  of  the  Amoebae.  The  water  drops  are 
ejected  at  a  spot  in  the  cell  membrane  just  below  the  gullet. 
If  a  little  finely  powdered  carmine  is  added  to  the  water 
in  which  the  Paramcecia  are  swim- 
ming some  of  the  grains  will  be  taken 
into  the  body  where  they  will  be  seen 
to  follow  a  rather  definite  course  from 
one  end  of  it  to  the  other.  Instead  of 
one  contractile  vacuole  as  in  the 
Amcebae  there  are  two,  and  there  are 
also  two  nuclei,  which  can  be  seen  in 
specimens  stained  with  carmine.  The 
large  one,  ovoid  in  shape,  is  called  the 
macronucleus,  and  the  smaller  oval 
one  close  beside  it  is  the  micronucleus. 
Between  the  bases  of  the  cilia  there 
may  be  seen  many  minute  oval  sacs 
lying  side  by  side.  These  are  called 
the  trichocysts,  and  from  each  a  fine 
stinging  thread  can  be  thrust  out 
which,  it  is  believed,  help  to  protect 
the  Paramcecium  from  other  minute 
animals. 

The  Paramcecia  reproduce  by  sim- 
ple division  as  do  the  Amcebae.  The 
macro-  and  micro-nuclei  divide  and 
the  body  becomes  constricted  in  the 
middle  and  the  organism  is  finally 
divided  into  two  smaller  animals  which 
soon  grow  to  be  like  the  original. 
But  after  multiplication  has  gone  on  in  this  way  for  many 
generations,  often  from  one  to  two  hundred  or  more,  the  Para- 
mcecia seem  to  be  unable  to  divide  further  until  a  new  pro- 
cess takes  place.  Two  Paramcecia  approach  each  other  and 
unite,  usually  with  their  buccal  grooves  together;  then  there 


FIG.  9. — Paramcecium 
sp.  Buccal  groove  at 
right.  (Greatly  magni- 
fied; from  life.) 


ONE-CELLED  ANIMALS 


31 


is  a  breaking  up  of  the  nuclei  and  a  part  of  the  micronucleus 
of  each  individual  passes  over  to  the  other.  Then  the  Para- 
moecia  separate  and  each  divides  into  two.  This  is,  in  very 
simple  condition,  the  process  of  ferti- 
lization, which  occurs  in  more  elaborate 
condition  in  all  the  higher  animals. 

Vorticella. — Many  other  minute  or- 
ganisms will  be  found  in  the  drops  of 
water  that  have  been  examined  while 
looking  for  the  Amoebae  and  Paramce- 
cia,  but  of  these  we  wish  to  call  parti- 
cular attention  to  but  one.  On  the 
leaves  or  sticks  that  have  been  collected 
from  ponds  and  placed  in  vessels  of 
water,  tiny  whitish  mould-like  tufts 
may  sometimes  be  seen.  Touch  such 
a  spot  with  a  needle  and  it  may  con- 
tract instantly.  If  so,  it  is  probably 
a  colony  of  Vorticella,  or  bell  animal- 
cules. Such  a  mass,  examined  under 
the  lens,  will  be  seen  to  be  made  up  of 
a  number  of  attached  slender  stalks 
each  having  a  bell-shaped  free  end, 
hence  the  common  name,  bell  animal- 
cule. When  the  stalk  is  extended  it  is 
straight  or  somewhat  curved  but  when 
the  animal  is  disturbed  the  stalk  con- 
tracts into  a  close  spiral.  The  thick- 
ened upper  outer  margin  of  the  bell, 
the  peristome,  and  the  central  disk,  the 
epistome,  are  fringed  with  rather  long 
cilia.  Between  the  peristome  and  the 
epistome  is  a  groove,  the  mouth  or  vesti- 
bule, which  leads  into  the  body.  The  substance  comprising 
the  body  is  differentiated  into  an  outer  uniformly  granular 
ectosarc  and  a  more  transparent,  colorless  endosarc,  in  which 
are  numerous  large  food  vacuoles,  a  large  clear  contracting 
vesicle,  a  large  curved  macro-nucleus,  and  near  it  a  micro- 


F I  G  .  i  o . —  Vorticella 
sp.  One  individual  with 
stalk  coiled,  and  one 
with  stalk  extended. 
(From  life;  greatly  mag- 
nified.) 


32      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

nucleus,  the  latter  often  being  difficult  to  see  unless  the 
specimens  are  stained.  The  slender  stalk  is  made  up  of  a 
clear  outer  portion  and  a  denser  contractile  inner  rod. 

The  Vorticellae  multiply  by  longitudinal  division,  or  fission. 
In  this  process  a  cleft  first  appears  at  the  distal  end  of  the  bell- 
shaped  body  and  gradually  deepens  until  the  original  body  is 
divided  quite  in  two.  The  stalk  also  divides  for  a  very  short 
distance.  One  of  the  new  bell-shaped  bodies  develops  a 
circlet  of  cilia  near  the  stalked  end.  After  a  while  it  breaks 
away  and  swims  about  by  means  of  this  basal  circlet  of  cilia. 
Later  it  settles  down,  becomes  attached  by  its  basal  end,  loses 
its  basal  cilia  and  develops  a  stalk.  Conjugation  sometimes 
occurs  between  two  individuals.  Under  certain  conditions 
there  is  produced,  by  repeated  divisions,  small  free-swimming 
forms,  one  of  which  may  meet  one  of  the  large  stalked  forms 
and  be  completely  absorbed  by  it.  This  differs  from  the  proc- 
ess of  fertilization  in  the  Paramoscia  in  which  the  union  was 
only  temporary,  and  presents  an  even  more  striking  analogy 
with  the  process  of  sexual  reproduction  occurring  in  the  higher 
animals. 

Marine  Protozoa. — The  Protozoa  are  more  abundant  in 
the  ocean  than  they  are  in  fresh  water.  Although  the  ocean 
water  may  appear  to  the  unaided  eyes  as  clear  and  free  from 
living  things,  yet  a  microscopical  examination  will  show  it  to 
be  swarming  with  minute  animals  and  plants.  These  are 
found  at  all  depths,  from  the  surface  to  the  deepest  parts  of 
the  ocean,  and  are  interesting  not  only  because  they  repre- 
sent the  lowest,  simplest  and  doubtless  earliest  kinds  of  ani- 
mals that  appeared  on  the  earth,  but  because  they  furnish, 
together  with  the  Protophyta,  or  one-celled  plants,  directly  or 
indirectly,  food  for  all  of  the  other  animals  of  the  sea.  As  we 
study  some  of  the  representatives  of  the  higher  groups  of  ocean 
animals  we  shall  see  that  many  of  them  are  particularly  adapted 
by  structure  and  habit  for  feeding  on  these  minute  organisms, 
and  that  they  in  turn  serve  as  food  for  other  animals,  so 
that  finally  all  of  the  animal  life  in  the  ocean  becomes  de- 
pendent on  the  one-celled  organisms  for  their  food.  This  is 
one  of  the  reasons  for  believing  that  the  Protozoa  were  the  first 


ONE-CELLED  ANIMALS 


33 


animals  to  appear  on  the  earth,  and  as  ocean  life  is  older 
than  terrestrial  life  it  is  probable  that  certain  marine  Protozoa 
are  the  most  ancient  of  all  animals. 

Some  of  these  marine  Protozoa,  as  the  Foraminifera  and  the 
Radiolaria,  secrete  a  tiny  shell  of  lime  or  silica  which  encloses 
most  of  the  body.  When  these  animals  die  their  shells  sink 
to  the  bottom  where,  as  they  slowly  accumulate,  they  form  a 
thick  layer  over  the  floor  of  large  areas  of  the  ocean.  The 


FIG.  ii. — A   marine   Protozoan,   Rosalind  varians    (Foraminifera),  with 
calcareous  shell.     (Greatly  magnified;  after  Schultze.) 

ooze  thus  formed  is  called  Foraminifera  ooze  or  Radiolaria  ooze, 
according  to  which  order  of  Protozoa  chiefly  formed  it.  All 
over  the  world  are  found  great  strata  of  rocks  that  are  formed 
almost  exclusively  of  the  fossil  shells  of  these  Protozoa.  The 
extensive  chalk  beds  and  cliffs  of  England,  France,  Greece, 
Spain  and  America  were  made  by  Foraminifera,  whose  shells 
were  deposited  there  when  these  places  wrere  parts  of  the  ocean 
beds.  The  siliceous  rock  called  Tripoli,  found  in  Sicily,  and  the 
Barbadoes  earth  from  the  island  of  Barbadoes  are  composed  of 
the  shells  of  ancient  Radiolaria. 

3 


34      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Parasitic  Protozoa. — Because  of  their  simple  structure  and 
physiology  the  Protozoa  easily  adapt  themselves  to  new  modes 
of  life,  when  conditions  are  favorable.  It  was  an  easy  step 
from  an  existence  in  the  water  to  life  in  the  blood  tissues  of 
some  of  the  aquatic  animals  or  in  some  of  the  higher  animals, 
and  the  Protozoa  that  have  made  this  step  have  come  to  be 
among  the  greatest  scourges  that  affect  mankind.  These 
parasitic  Protozoa  are  so  important  that  a  later  separate 
chapter  will  be  deviated  to  an  account  of  them.  (See  Chapter 
XXVIII.) 

Classification  of  the  Protozoa. — The  branch  Protozoa  is 
divided  into  five  groups  or  classes,  the  divisions  being  based 
principally  on  the  manner  in  which  the  members  of  the  different 
groups  move  about.  The  Amoeba,  the  Foraminifera  and  the 
Radiolaria  belong  to  the  class  Rhizopoda  (Gr.  rhiza,  root; 
POUS,  foot).  Rhizopoda  means  "root-footed"  and  the  name 
is  applied  to  those  Protozoa  which  move  about  by  means  of 
the  extending  or  flowing  out  of  the  root-like  processes  called 
pseudopodia,  or  false  feet. 

Paramcecium  and  Vorticella  belong  to  the  class  Infusoria 
(L.  infusus,  infused),  a  name  that  was  early  used  because 
these  organisms  are  so  frequently  found  in  infusions.  Because 
their  body  is  furnished  with  minute  hair-like  organs  called 
cilia  they  are  often  called  Ciliata. 

From  an  economic  point  of  view  the  class  Sporozoa  (Gr. 
spora,  seed;  zoon,  animal)  is  the  most  important.  The  mem- 
bers of  this  class  are  parasitic  and  cause  some  of  the  most 
serious  diseases  of  man  and  other  animals,  such  as  the  various 
malarial  fevers,  the  spotted  fever  of.  man,  and  the  Texas  fever 
of  cattle. 

The  whip-bearers  (class  Mastigophora,  Gr.  mastix,  whip; 
phero,  bear)  also  include  a  number  of  important  parasites,  as 
the  trypanosomes  that  are  the  cause  of  the  dreadful  disease 
which  ends  in  sleeping  sickness,  and  the  Spirochcetce,  which  are 
the  cause  of  certain  relapsing  fevers.  The  little  green  Euglena, 
whose  presence  in  standing  pools  often  imparts  a  greenish 
color  to  the  water,  and  the  wonderfully  phosphorescent 
Noctiluca  of  ocean  waters,  also  belong  to  this  class.  The 


ONE-CELLED  ANIMALS  35 

Noctiluca  live  near  the  surface,  and  when  disturbed  at  night 
their  little  bodies  glow  like  coals  of  fire.  This  class  also  in- 
cludes a  number  of  so-called  colonial  Protozoa  such  as  Volvox, 
Proterospongia  and  others.  These  are  more  or  less  closely 
associated  groups  of  similar  individuals  or  colonies  in  which  the 
individual  members  show  some  differences  and  have  more  or 
less  special  functions  to  perform. 

The  members  of  the  class  Mycetozoa  (Gr.  mykes,  fingers; 
zoon,  animal)  resemble  fungi  in  many  respects  and  are  often 
included  with  them  under  the  name  "slime  moulds."  They 
are  of  no  economic  importance. 

Protoplasm  and  the  Cell. — All  the  Protozoa  have  the  body 
composed,  for  its  whole  life,  of  but  a  single  cell.  By  cell  is 
meant  not  necessarily  a  little  enclosed  or  box-like  bit  of  animal 
substance,  but  simply  a  small  (usually  microscopic)  mass  of 
protoplasm  which  is  composed  of  an  inner,  denser  part  called 
nucleus  and  a  surrounding  less  dense  part  called  cytoplasm. 
Protoplasm  itself,  "  the  physical  basis  of  life,"  is  a  substance  or 
group  of  substances,  usually  viscous  or  jelly-like,  which  always 
contains  certain  very  complex  albuminous  chemical  compounds 
called  proteins.  These  proteins  are  never  found  in  inorganic 
matter  and  are  always  fround  in  living  tissues.  Proteins 
contain  carbon,  oxygen,  hydrogen  and  nitrogen,  and  are 
almost  the  only  group  of  substances  found  in  living  matter  of 
which  chemists  have  not  yet  been  able  to  make  representatives 
in  the  laboratory.  Besides  the  all-important  proteins  proto- 
plasm usually  includes  certain  other  characteristic  compounds 
known  as  carbohydrates  and  fats  (which  contain  no  nitrogen), 
and  various  salts  and  gases,  and  always  water.  The  gases  are 
oxygen  and  carbon  dioxide,  and  the  salts  are  compounds  of 
chlorine  as  well  as  the  carbonates,  sulphates  and  phosphates  of 
the  alkalies  and  alkali  earths.  Common  salt  (sodium  chloride) 
is  almost  always  present. 

What  a  Single  Cell  Can  Do. — All  the  larger  animals  are  com- 
posed of  many  cells  which  are  grouped  together  to  form  organs 
or  tissues  each  with  its  special  function  to  perform,  but  the 
minute  one-celled  mass  or  protoplasm  forming  the  whole 
body  of  each  Protozoan  is  able  to  carry  on  all  the  necessary 


36      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

processes  of  life,  digestion,  assimilation,  respiration,  excretion, 
secretion,  and  to  reproduce  others  of  its  kind.  It  is  this 
wonderful  capacity  for  living  that  separates  the  one-celled 
organisms,  simple  as  they  may  seem  to  be  in  comparison  with 
higher  plants  and  animals,  by  a  wide  gulf  from  the  most  com- 
plex of  inorganic  bodies.  Some  scientists  have  been  able  to 
produce  in  their  laboratories  particles  of  matter  that  closely 
resemble,  in  many  respects,  these  simple  organisms,  but  none 
has  yet  been  able  to  endow  these  creations  with  the  subtle 
power  which  we  call  life. 

We  have  found,  moreover,  in  our  study  of  the  Protozoa  that 
while  they  are  each  composed  of  but  a  single  cell,  or,  rarely,  of 
a  group  of  cells  temporarily  united  to  form  a  colony,  the  cell 
itself  may  be  very  complex  in  its  structure,  some  parts  of  it 
adapted  for  protection,  other  parts  for  locomotion  or  food 
getting.  There  may  be  a  definite  upper  and  lower  side  and 
anterior  and  posterior  end,  and  there  may  be  many  other 
specializations  of  parts  that  especially  fits  each  of  these  one- 
celled  animals  to  live  in  its  particular  place. 

Spontaneous  Generation. — People  used  to  believe  that  many 
animals  were  spontaneously  generated.  When  myriads  of  fly 
larvae  mysteriously  appeared  in  a  mass  of  decaying  matter  it 
was  supposed  that  they  had  been  generated  there  spontane- 
ously. When  great  numbers  of  frogs  or  insects  or  any  other 
animals  appeared  from  some  unknown  source  the  phenomenon 
was  explained  by  spontaneous  generation.  Long  after  it  had 
definitely  been  shown  that  none  of  the  larger  animals  could 
arise  in  this  way,  many  still  held  to  the  belief  that  at  least  the 
simplest  animals  and  plants  arose  in  this  way.  If  a  vessel  of 
ordinary  water  in  which  there  are  apparently  no  living  organ- 
isms be  allowed  to  stand  for  a  few  days  it  will  usually  be  found 
to  be  swarming  with  minute  animals  and  plants.  The  source 
of  this  life  was  a  mystery  to  the  older  observers,  but  we  know 
now  that  some  of  these  organisms  come  from  others  that  were 
already  in  the  water  and  some  come  from  spores  that  are 
constantly  in  the  air.  If  a  bottle  of  water  is  boiled  thoroughly 
enough  to  kill  all  the  organisms  in  it,  and  then  closed  so  tightly 
that  no  germs  or  spores  can  reach  it  from  the  outside,  it  will 


ONE-CELLED  ANIMALS 


37 


remain  perfectly  sterile    that  is,  no  living  animal  nor  plant 
will  ever  appear  in  it. 

Reproduction  in  Protozoa. — All  life  comes  from  life.  Every 
living  creature  is  the  offspring  of  some  other  living  creature. 
This  is  just  as  true  for  the  Protozoa  as  for  the  higher  animals, 
but  their  method  of  reproduction  is  usually  much  more  simple. 
In  many  cases  the  Protozoan  animal  simply  divides  into  two 
more  or  less  similar  smaller  animals  which  grow  until  they 
attain  a  certain  size  and  then  divide  again,  and  the  process  is 
continued  for  generation  after 
generation.  This  is  called  repro- 
duction by  simple  division  or  fis- 
sion. 

Protozoa  that  thus  live  and  re- 
produce by  simple  division  have 
been  called  immortal,  and  it  would 
seem  that  under  natural  condi- 
tions such  animals  never  die,  for 
as  soon  as  they  reach  a  certain 
size  they  divide  and  form  two  new 
individuals  and  as  this  process  is 
continued  for  generation  after  gen- 
eration there  would  seem  to  be  no 
death  of  the  individual.  Careful 
studies  have  shown,  however,  that  this  process  of  simple  divi- 
sion cannot  continue  indefinitely  unless  there  is  introduced 
into  the  cycle  from  time  to  time  the  extraordinary  process 
known  as  fertilization  by  which  the  mature  or  old  individuals 
are  rejuvenated.  In  many  of  the  Protozoa  this  process  of 
fertilization  is  accomplished  by  the  conjugation  of  two  similar 
individuals  in  which  two  animals  come  together  and  undergo 
complete  or  temporary  fusion.  Such  a  conjugation  is  followed 
by  renewed  activity,  the  process  of  division  going  on  more 
rapidly  than  before. 

Many  Protozoa  instead  of  dividing  directly  into  two  parts 
go  through  a  process  called  spore  formation.  The  animal 
becomes  encysted  in  a  firm  little  sac  or  cyst  in  which  it  remains 
for  some  time.  Then  it  divides  into  many  small  bodies,  called 


FIG.  12.  —  Division  of 
Amoeba.  (Greatly  magnified; 
after  Schultze.) 


3 8      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

spores,  which  finally  burst  out  into  the  water  or  other  medium 
in  which  the  animal  lives,  where  each  spore  develops  into  an 
organism  like  the  parent.  This  process  makes  it  possible  for 
the  animals  to  multiply  very  rapidly,  and  we  shall  see  something 
of  its  importance  when  we  come  to  study  the  Sporozoa,  a  group 
of  parasitic  Protozoa  which  all  reproduce  in  this  way  and  some 
of  which  are  the  causes  of  certain  common  diseases  of  man  and 
other  animals. 


CHAPTER  VII 
ONE-CELLED  AND  MANY-CELLED  ANIMALS 

Of  the  animals  so  far  studied,  Amoeba,  Paramoecium, 
Vorticella  and  their  allies  have  the  minute  body  composed  of 
but  a  single  cell.  The  others,  the  frog,  grasshopper  and  hydra, 
have  the  body  composed  of  many  cells.  This  distinction  of 
one-celled  and  many-celled  body  has  led  to  the  classification 
of  all  animals  into  two  primary  groups,  the  Protozoa,  including 
all  those  with  one-celled  body,  and  the  Metazoa,  all  those 
with  a  many-celled  body.  They  are  groups  of  very  unequal 
size,  as  of  the  500,000  (approximated)  known  kinds  of  living 
animals  all  but  about  10,000  are  Metazoa.  But  the  distinction 
between  Protozoa  and  Metazoa  is  very  important;  it  is  indeed 
one  of  the  most  fundamental  in  animal  structure  and  classifica- 
tion. For  although  many-celled  animals  are  undoubtedly 
derived  by  descent  from  one-celled  ones,  yet  the  group  of  single- 
celled  animals,  the  Protozoa,  is  much  larger  than  we  should 
expect  it  to  be  if  it  were  simply  the  beginning  of  the  animal 
scale.  It  is  not  only  a  beginning  stage  in  animal  evolution, 
but  it  is  an  evolutionary  line  of  its  own.  There  is  a  great  deal 
of  variety  and  complexity  in  the  structure,  physiology  and 
mode  of  development  within  the  protozoan  branch.  All  this 
diversity  has,  however,  to  be  limited  to  the  differences  possible 
to  a  single  cell.  The  moment  animal  evolution  made  the  step 
from  independent  single  cell  to  mutually  dependent  many  cells, 
united  for  life,  infinitely  greater  possibilities  of  diversity  in 
structure  and  function  and  life  history  were  open.  And  the 
extraordinary  variety  of  animal  life  as  it  appears  to  us  now  in 
the  various  groups  of  Metazoa,  is  the  result  of  Nature's  taking 
advantage  of  these  possibilities. 

But  the  step  was  not  a  sharp  one,  nor  was  the  attainment  of 
present-day  animal  complexity  and  diversity  brought  about 

39 


40      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

at  all  speedily.  It  was  millions  of  years  after  the  first 
many-celled  animals  appeared  on  the  earth  before  the  first 
insect  appeared.  And  still  millions  of  years  later  before  the 
first  backboned  animal  was  evolved. 

As  to  the  step  from  isolated  single  cell  to  united  many  cells, 
it  was  undoubtedly  made  in  the  simple  way  still  represented 
by  a  few  living  organisms  known  as  Volvocinae,  sometimes 
called  plants,  and  sometimes  animals.  These  are  one-celled 
organisms  that  live  as  small  colonies  or  groups  of  cells.  These 
few  cells,  only  sixteen  in  the  case  of  several  of  these  organisms, 
are  all  derived  from  a  single  cell  by  its  division  into  two  and  the 
succeeding  divisions  of  these  two  into  four,  the  four  into  eight 
and  the  eight  into  sixteen.  And  they  are  all  alike.  They 
remain  together  in  the  form  of  a  tiny  ball,  the  cells  all  imbedded 
in  a  soft  gelatinous  substance  secreted  by  them.  Each  cell  has 
a  pair  of  flagella,  and  the  waving  of  all  the  flagella  moves  the 
little  ball  through  the  water.  Each  cell  can  take  up  food, 
respond  to  stimuli,  and  in  fact  do  all  the  things  that  we  have 
found  are  essential  to  living  and  which  are  done  in  the  simplest 
manner  by  the  one-celled  animals.  Indeed  it  is  probable  that 
each  cell  could  live  independently;  and  as  a  matter  of  fact  each 
one  does  for  a  short  time  when  the  colony  breaks  up  after  reach- 
ing maturity. 

For  when  this  little  colony  is  mature  and  ready  to  repro- 
duce itself,  the  gelatinous  stuff  dissolves,  the  sixteen  cells 
are  set  free  in  the  water,  and  each,  by  repeated  division  may 
produce  a  new  colony.  Or  a  process  of  conjugation  between 
pairs  of  the  freed  cells  can  take  place,  and  from  each  paired 
cell  formed  by  the  conjugation  of  the  two,  a  new  colony  may 
be  formed  by  simple  division. 

Differentiation  and  Specialization  of  Cells. — If  this  first  step 
toward  making  a  many-celled  animal  out  of  a  single-celled  one 
seems  simple,  the  next  step  does  not.  In  the  simplest  kinds  of 
true  many-celled  animals  an  important  new  condition  appears. 
It  is  a  condition  of  differentiation  or  specialization  of  the  cells 
united  to  form  the  body.  The  cells  are  no  longer  all  alike  in 
appearance,  and  no  longer  have  identical  capacities.  Only  a 
few  of  them  remain  in  simple  generalized  condition.  These 


ONE-CELLED  AND  MANY-CELLED  ANIMALS    41 

are  the  so-called  white  blood  corpuscles  which  have  an  appear- 
ance much  like  that  of  the  Amoebae  and  have  a  great  deal  of 
freedom  or  independence  in  their  life. 

The  rest  of  the  hundreds  or  thousands  or  millions  of  cells  that 
go  to  make  up  a  many-celled  animal's  body  differ  greatly 
in  appearance  and  behavior  from  Amoebae,  and  differ  also 
greatly  among  themselves.  Besides  the  amoeboid  white  cells 
in  the  blood  there  are,  in  red-blooded  animals,  many  elliptical, 
disk-like  reddish  cells  and  they  have  an  entirely  different  func- 
tion from  that  of  the  white  cells.  The  cells  composing  the 
muscles  are,  moreover,  not  like  either  of  the  kinds  of  blood 
cells;  the  cells  of  which  the  liver  is  composed  are  not  like  the 
cells  of  the  muscles;  and  the  cells  which  compose  the  organs  of 
the  nervous  system,  brain,  ganglia  and  nerves,  differ  markedly 
from  those  of  the  blood,  muscles  and  liver,  and  differ  also  very 
much  among  themselves. 

Each  of  these  kinds  of  cells,  and  each  of  the  many  other  kinds 
that  exist  in  the  body  of  one  of  the  higher  animals,  has  become 
specialized  in  order  to  devote  itself  to  a  certain  particular  func- 
tion or  special  work.  For  example,  the  cells  of  the  nervous 
system  devote  themselves  to  the  function  of  receiving  and 
transmitting  sensation.  The  muscle  cells  have  developed  to 
a  high  degree  the  power  of  contractility,  and  they  have  for  their 
special  function  this  one  of  contraction.  Massed  together  in 
great  numbers,  they  form  the  strongly  contractile  muscles  of 
the  body  on  which  the  animal's  power  of  motion  depends. 
The  cells  which  line  certain  parts  of  the  alimentary  canal  are 
the  ones  on  which  the  function  of  digestion  largely  rests.  And 
so  we  might  continue  our  survey  of  the  whole  complex  animal 
body.  The  point  of  it  all  is,  however,  that  the  thousands  of 
cells  which  compose  many-celled  animal  bodies  are  differenti- 
ated and  specialized.  That  is,  have  become  changed  or  modi- 
fied from  the  generalized  primitive  amoeboid  cell  condition  so 
that  each  kind  of  cell  is  devoted  to  some  special  work  or  func- 
tion, and  has  a  special  structural  character  fitting  it  for  its 
special  function. 

Organs  and  Functions. — The  specialized  cells  are  grouped 
into  tissues  and  organs.  These  organs  are  known  to  us 


42      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

familiarly  as  various  parts  of  the  body,  such  as  lungs,  heart, 
muscles,  eyes,  stomach,  etc.  The  life  of  an  animal  consists  of 
the  performance  by  it  of  various  processes,  such  as  breathing, 
getting  and  digesting  food,  circulating  blood,  moving,  seeing, 
etc.  These  various  processes  or  functions  are  performed  by 
the  various  parts  or  organs  of  the  body. 

The  whole  body  of  a  many-celled  animal  is  thus  really  a 
machine  composed  of  various  parts,  each  part  with  its  special 
work  to  do  but  all  depending  upon  one  another  and  operating 
to  accomplish  the  work  of  living.  The  locomotive  engine  is  a 
machine  similarly  composed  of  various  parts,  each  part  with 
its  special  work  or  function,  and  all  the  parts  depending  on  one 
another  and  so  working  together  as  to  perform  satisfactorily 
the  work  for  which  the  locomotive  engine  is  intended.  An 
important  difference  between  the  locomotive  engine  and  the 
animal  body  is  that  one  is  a  lifeless  machine  and  the  other  a 
living  machine.  But  there  is  a  real  similarity  between  the 
two  in  that  both  are  composed  of  special  parts,  each  part 
performing  a  special  kind  of  wrork  or  function,  and  all  the  parts 
and  functions  so  fitted  together  as  to  form  a  complex  machine 
which  successfully  accomplishes  the  work  for  which  it  is 
intended.  And  this  similarity  is  one  which  should  help  make 
plain  the  fundamental  fact  of  animal  structure  and  physiol- 
ogy, namely,  the  division  of  the  body  into  numerous  parts  or 
organs,  and  the  division  of  the  total  work  of  living  into  various 
processes  which  are  the  special  work  or  functions  of  the  various 
organs. 

Essential  and  Accessory  Life  Processes. — A  very  complex 
animal,  such  as  a  dog,  performs  a  great  many  different  func- 
tions, that  is,  does  a  great  many  different  things  in  its  living. 
But  there  are  many  animals  in  which  the  body  is  composed  of 
but  a  few  parts  and  whose  life  includes  the  performance  of 
fewer  functions  or  processes  than  in  the  case  of  a  dog.  There 
are  many  animals  that  have  no  eyes,  nor  ears,  nor  organs  of 
special  sense.  There  are  animals  without  legs  or  other  special 
organs  of  locomotion;  some  animals  have  no  blood  and  hence 
no  heart  nor  arteries  and  veins.  But  in  the  life  of  every  animal 
there  are  certain  processes  which  must  be  performed,  and  the 


ONE-CELLED  AND  MANY-CELLED  ANIMALS    43 

body  must  be  so  arranged  or  composed  as  to  be  capable  of 
performing  these  necessary  life  processes.  •  All  animals  take 
food,  digest  it  and  assimilate  it,  that  is,  convert  it  into  new  body 
substance;  all  animals  take  in  oxygen  and  give  off  carbon 
dioxide;  all  animals  have  the  power  of  movement  or  motion 
(not  necessarily  locomotion);  all  animals  have  the  power  of 
sensation,  that  is,  can  feel;  all  animals  can  reproduce  them- 
selves, that  is,  produce  young.  These  are  the  necessary  life 
processes.  It  is  evident  that  the  dog  could  still  live  if  it  had 
no  eyes.  Seeing  is  not  one  of  the  necessary  functions  or  proc- 
esses of  life.  Nor  is  hearing,  nor  is  leaping,  nor  are  many  of 
the  other  things  which  the  dog  can  do;  and  animals  can  exist, 
and  do  exist,  without  any  organs  to  enable  them  to  see  and  hear 
and  leap.  But  the  body  of  an  animal  must  be  capable  of 
performing  the  few  essential  processes  which  are  necessary  to 
animal  life.  How  surprisingly  simple  such  a  body  can  be  our 
study  of  the  Protozoa  has  already  shown.  But  in  most  animals 
the  body  is  a  complicated  object,  and  is  able  to  do  many  things 
which  are  accessory  to  the  really  essential  life  processes,  and 
which  make  its  life  complex  and  elaborate. 

The  Principal  Systems  of  Organs  and  Functions. — These 
complex  life  processes  are  usually  carried  on  by  systems  of 
organs  which  are  known  as  the  skeletal,  muscular,  digestive, 
respiratory,  circulatory,  excretory,  nervous  and  reproductive 
systems.  And  the  particular  set  of  special  functions  or  life 
processes  connected  with  each  is  sufficiently  indicated  by  its 
name.  Of  them  all,  the  reproductive  system  and  its  function, 
which  is  that  of  the  multiplication  of  the  species,  calls  for  a  few 
special  words  of  introduction  before  we  pass  to  the  considera- 
tion of  the  successive  animal  groups.  For  it  is  in  connection 
with  this  function  that  some  of  the  most  important  special 
conditions  in  animal  life  exist.  The  important  fact  of  sex,  for 
example,  is  correlated  with  this  function,  while  the  whole 
subject  of  animal  development  may  be  looked  on  as  part  of 
the  study  of  animal  multiplication. 

Reproduction  and  Development  in  the  Metazoa. — We  have 
learned  that  the  process  of  multiplication  among  the  Protozoa 
is,  in  most  cases,  very  simple,  consisting  of  the  simple  splitting 


44      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

of  the  parent's  body  in  two.  Previous  to  this  splitting  in  two 
there  may  be  a  temporary  fusion  for  the  purpose  of  a  mutual 
exchange  of  part  of  the  body  substance,  or  a  permanent  con- 
jugation of  two  individuals.  The  process  of  reproduction 
among  the  many-celled  animals  is  far  more  complex,  and  certain 
particular  organs  of  the  body  of  complex  structure  are  specially 
devoted  to  this  function.  The  results  of  the  process,  however, 
are  the  same  as  among  the  lower  animals,  namely,  the  produc- 
tion of  new  individuals.  The  manner  in  which  the  reproduc- 
tive process  is  carried  on,  and  the  number  of  new  individuals 
produced  by  a  single  parent  individual,  may  and  do  vary  much 
among  different  animals. 

Among  some  of  the  simpler  many-celled  animals  the  new 
individual  is  sometimes  produced  by  the  growth  of  an  external 
bud,  or  by  the  splitting  off  of  a  small  part  of  the  parent's  body, 
a  process  much  like  the  fission,  or  splitting  in  two,  of  the  one- 
celled  animals.  But  this  is  an  unusual  method,  and  possible 
to  comparatively  few  animals.  In  almost  all  cases  the  young 
come  from  eggs,  or  ova,  which  are  produced  inside  the  body  of 
the  mother.  These  eggs  usually  issue  from  the  body  before 
hatching,  but  in  some  animals,  as  all  the  Mammalia,  the  young 
develop  from  the  ova  inside  the  body  and  are  born  as  active 
free  animals,  resembling  the  parent  more  or  less  in  appearance 
and  structural  character,  although  of  course  much  smaller. 

In  all  cases  the  young  animal  has  to  undergo  a  certain  amount 
of  development  and  growth,  which  extends  over  a  longer  or 
shorter  period  of  time,  before  it  is  really  like  its  parent,  that  is, 
before  it  is  a  fully  developed,  full-grown  individual.  No 
animal  is  born  fully  developed;  it  is  born  from  the  body  of  its 
mother  or  hatched  from  its  egg  in  an  immature  condition,  and 
growth  and  change  are  necessary  before  we  have  a  fully  devel- 
oped rabbit  or  robin,  or  any  other  kind  of  animal. 

But  when  we  begin  the  study  of  the  life  history  of  the  new 
animal  with  the  time  of  its  emergence  from  the  body  of  the 
mother  or  from  the  egg,  we  are  not  beginning  at  the  beginning. 
When  we  first  see  the  new  animal  it  is  already  of  appreciable 
size  and  complex  structure.  But  at  its  very  beginning  inside 
the  body  of  the  mother  it  is,  in  every  case,  simply  a  single  cell. 


ONE-CELLED  AND  MANY-CELLED  ANIMALS    45 

Every  individual  begins  as  a  single  cell,  and  develops  and  grows 
from  this  single  cell  to  its  final  complex  adult  condition.  The 
first  single  cell  is  called  the  fertilized  egg  cell  or  ovum,  and  an 
egg  is  simply  this  primary  germ  cell,  or  the  embryo  which 
develops  from  it,  together  with  a  greater  or  less  amount  of 
yolk  (which  is  food  for  the  germ),  enclosed  in  a  membrane  or 
shell.  In  the  case  of  those  animals  which  do  not  lay  eggs,  but 
give  birth  to  their  young  in  a  free  condition,  the  egg,  which  is 
kept  inside  the  body  of  the  mother,  is  usually  composed  of  the 
germ  alone,  food  being  provided  the  embryo  directly  from  the 
body  of  the  mother.  After  the  young  has  reached  a  certain 
stage  in  its  development,  it  leaves  the  body  of  the  mother  and 
food  is  provided  it  by  suckling  or  in  some  other  way.  The 
development  of  an  animal  from  first  germ  cell  to  the  time  it 
leaves  the  body  of  the  mother,  if  born  free,  or  until  it  is  hatched 
from  an  egg,  is  called  its  embryonic  development;  and  the 
development  from  then  on  is  called  the  post-embryonic  develop- 
ment. Beginning  students  of  zoology  cannot  study  the  em- 
bryonic development  (embryology)  of  animals  readily,  but  they 
can  in  many  cases  follow  the  course  of  the  post-embryonic 
development,  and  this  study  will  always  be  interesting  and 
valuable 

It  is  a  kind  of  study  of  particular  importance  to  the  economic 
zoologist,  because  in  all  attempts  to  make  better  uses  of  animals, 
or  to  restrain  their  injuries,  a  knowledge  of  their  life  history  is 
essential.  This  life  history  includes  the  facts  of  their  develop- 
ment and  the  facts  of  their  habits  and  general  behavior  both 
in  immature  and  mature  condition.  In  the  case  of  an  injurious 
insect,  for  example,  the  times  and  place  of  egg-laying,  the 
character  and  duration  of  the  immature  stages,  the  time  and 
place  of  pupation,  etc.,  are  all  important  conditions.  A 
knowledge  of  these  may  enable  the  economic  zoologist  to  hit 
upon  exactly  the  best  means  for  combating  the  pest. 

The  radical  changes  or  metamorphoses  undergone  during 
development  by  many  insects  must  be  taken  into  account  in 
any  consideration  of  them  as  possible  enemies  of  man.  Young 
grasshoppers,  for  example,  are  wingless  and  can  be  captured 
and  killed  by  simple  methods  which  would  be  of  no  use  in  the 


46      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

case  of  the  mature  flying  individuals.  Indeed  even  simpler 
and  more  effective  means  can  be  brought  to  bear  against  the 
eggs  of  the  grasshoppers.  But  a  knowledge  of  the  times, 
places  and  peculiar  manner  of  the  egg-laying  of  grasshoppers 
was  necessary  as  a  basis  for  devising  these  remedies.  Butter- 
flies and  moths  take  only  plant  nectar  and  water  for  food,  and 
are  harmless — in  the  adult  stage.  But  in  their  immature 
stage,  as  strong-jawed  biting  larvae  (caterpillars)  many  kinds 
are  extremely  injurious.  The  mosquito  is  annoying  as  a 
blood-sucking  pest  and  dangerous  as  a  breeder  and  disseminator 
of  yellow  and  malarial  fevers  only  as  a  full- developed  flying 
adult,  but  it  is  only  in  its  immature  or  larval  and  pupal  stages 
passed  in  quiet  water  that  it  can  be  successfully  fought.  The 
student  of  economic  zoology  then  should  give  a  special  atten- 
tion to  the  study  of  animal  multiplication  and  development. 

Sex  and  the  Fertilization  of  the  Egg. — Among  the  one-celled 
animals  we  found  that  before  an  individual  divided  into  two, 
that  is,  multiplied,  it  sometimes  met  another  individual  with 
which  it  exchanged  body  substance.  Among  most  of  the  many- 
celled  animals  the  germ  cell  or  fertilized  egg  cell  which  develops 
into  a  new  individual  is  produced  by  the  fusion  of  two  so-called 
reproductive  cells  from  two  distinct  individuals  of  the  same 
species  or  kind  of  animal. 

The  reproductive  cells  produced  by  the  females  are  known 
as  eggs  or  ova,  and  are  usually  produced  in  the  ovaries;  those 
produced  by  the  male  are  called  spermatozoa  and  are  produced 
in  the  spermaries,  or  testes.  Before  the  ova  can  begin  their 
development  they  must  be  fertilized  by  the  spermatozoa. 
There  are  a  few  exceptions  to  this  general  rule,  young  being 
produced  by  some  kinds  of  animals  from  unfertilized  eggs. 
But  these  cases  are  comparatively  rare  and  in  most  of  them 
fertilization  of  some  of  the  eggs,  at  least,  takes  place  also. 

We  shall  find  among  the  Metazoa  various  devices  to  aid  in 
bringing  the  ova  and  spermatozoa  of  two  individuals  of  a  kind 
together.  Many  of  the  aquatic  animals  simply  cast  their 
reproductive  cells  into  the  water  where  they  meet  by  chance. 
Of  course  many  of  the  ova  thus  thrown  out  are  never  reached 
by  the  spermatozoa  and  so  no  development  takes  place,  but 


ONE-CELLED  AND  MANY-CELLED  ANIMALS    47 

when  the  eggs  are  laid  in  this  way  they  are  always  produced 
in  great  numbers.  An  average  sized  oyster  will  produce 
during  the  season  about  16,000,000  eggs  and  a  large  old  female 
may  produce  more  than  three  times  that  many  during  the  few 
summer  months  that  she  is  breeding.  The  number  of  sper- 
matozoa that  are  produced  by  a  male  oyster  is  simply  incon- 
ceivable, and  the  water  in  the  vicinity  of  the  oyster  beds  is 
literally  swarming  with  these  minute  cells  during  the  breeding 
season.  These  enormous  numbers  are  made  necessary  by 
the  fortuitous  mode  of  fertilization.  It  is  a  condition  compar- 
able with  that  of  the  great  production  of  pollen  and  chance 
method  of  pollination  in  the  case  of  the  pines  and  other  wind- 
pollinated  flowers. 

Other  aquatic  animals,  as  certain  fishes,  lay  their  eggs  in  a 
more  or  less  carefully  prepared  nest,  and  the  male  soon  passes 
by  and  deposits  the  milt,  which  contains  the  spermatozoa, 
over  them.  With  most  of  the  higher  animals,  however,  the 
ova  are  fertilized  while  still  inside  the  body  of  the  mother,  and 
various  provisions  are  made  for  transferring  the  spermatozoa 
from  the  male  to  the  female. 


CHAPTER  VIII 
THE  CLASSIFICATION  OF  ANIMALS 

The  first  thing  one  asks  about  an  animal  new  to  one's  ex- 
perience is,  what  is  its  name?  It  is  really  less  the  name  itself 
that  we  wish  to  know,  than  the  information  that  this  name 
gives  regarding  the  placing  of  the  animal  in  some  classificatory 
relation  with  other  animals.  It  is  the  classifying  interest 
that  impels  our  question;  and  with  most  of  us  it  is  this  interest 
— which  in  turn  usually  develops  from  a  collecting  interest — 
that  first  attracts  us  to  the  study  of  zoology. 

Meaning  and  Basis  of  Classification. — However,  if  classify- 
ing animals  meant  only  arranging  them  in  simple1  groups  of 
similar  or  dissimilar  forms,  and  naming  them,  the  classificatory 
interest  would  deserve  the  reproaches  so  often  heaped  on  it 
by  naturalists  more  interested  in  anatomy  or  physiology  or 
development.  But  classifying  animals  means  much  more 
than  that.  Since  the  days  of  Darwin's  "Origin  of  Species," 
when  the  theory  of  the  evolution  of  animals  and  plants  was  so 
clearly  explained  and  proved  that  the  world  could  not  help 
but  accept  it  as  true,  the  classification  of  living  things  has  had 
a  new  and  great  importance.  It  has  the  importance  of  repre- 
senting our  knowledge  of  organic  evolution,  for  the  classifying 
of  animals  and  plants  now  means  arranging  them  in  groups 
according  to  their  descent. 

In  the  early  days  of  the  study  of  animals  and  plants  their 
classification  or  division  into  groups  was  based  on  the  external 
resemblances  and  differences  which  the  early  naturalists  found 
among  the  organisms  they  knew.  But  later  when  naturalists 
began  to  dissect  animals  and  get  acquainted  with  the  whole 
body,  the  differences  and  likenesses  of  the  inner  parts,  such 
as  the  skeleton  and  organs  of  circulation  and  respiration,  were 
taken  into  account.  For  we  know  that  animals  which  are 

48 


THE  CLASSIFICATION  OF  ANIMALS  49 

really  closely  related  may  not,  on  the  surface,  closely  resemble 
each  other.  The  outside  of  their  bodies  may  become  much 
modified  to  adapt  them  to  different  environments.  But  their 
internal  structure  and  their  development  will  usually  reveal 
their  nearness  or  relation.  On  the  other  hand,  animals  not 
closely  related  by  descent  may  become  and  look  superficially 
like  each  other  by  becoming  adapted  to  living  in  the  same 
environment,  taking  the  same  kind  of 'food,  etc.  But  again  a 
study  of  the  development  and  internal  anatomy  will  usually 
establish  marked  differences,  indicating  their  lack  of  real  gen- 
ealogic  nearness. 

Modern  zoological  classification,  is,  therefore,  based  on  a 
great  deal  of  serious  study  of  animal  structure  and  development 
and  represents,  as  we  have  already  said,  our  present  knowledge 
of  the  actual  blood  relationships  of  animals.  It  means  more 
than  that  animals  of  the  same  group  resemble  each  other  in 
certain  structural  characters.  It  means  that  the  members 
of  a  group  are  related  to  each  other  by  descent,  that  is  genealog- 
ically. They  are  all  the  descendants  of  a  common  ancestor; 
they  are  all  sprung  from  a  common  stock.  And  this  added 
meaning  of  classification  explains  the  older  meaning;  it  ex- 
plains why  the  animals  are  alike.  The  members  of  a  group 
resemble  each  other  in  structure  because  they  are  actually 
blood  relations. 

The  history  of  animal  classification  with  all  the  changes  in 
it,  and  the  succeeding  points  of  view  and  new  significance 
represented  by  these  changes,  is  an  interesting  chapter  in  the 
history  of  science.  It  began,  in  any  real  way,  with  Linnaeus, 
the  great  Swedish  naturalist  who  worked  in  the  middle  of  the 
eighteenth  century.  In  the  years  just  before  and  after  1750 
he  published  successive  editions  of  his  "Systema  Naturae," 
which  was  the  first  attempt  to  describe  and  name  and  classify 
all  the  known  kinds  of  animals  and  plants.  In  the  loth  edition 
(1758)  of  this  "Systema"  he  catalogued  about  4000  kinds  of 
animals.  (Now  we  know  500,000  kinds!) 

In  this  great  catalogue  he  adopted  a  system  of  short  scien- 
tific names,  one  for  each  kind  of  organism.  And  he  classified 
all  these  named  animals  into  groups  of  successive  degrees  of 

4 


50      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

inclusiveness,  which  he  called,  species,  genus,  ordo  and  classis. 
We  still  use  Linnseus's  general  system  of  classification  and  most 
of  his  short  two-word  scientific  names  for  the  different  animals 
and  plants  that  he  knew,  but  we  base  the  classification  on  other 
grounds  than  the  superficial  resemblances  that  he  used,  and  we 
see  in  our  classification  a  more  far-reaching  significance  and  a 
much  greater  importance  than  he  saw.  But  Linnaeus  was  the 
first  great  animal  classifier,  or  systematic  zoologist,  and  de- 
serves all  honor  for  his"  important  work. 

Animal  Names. — Well-known  animals  have  common,  or 
vernacular  names,  but  less  familiar  ones  do  not.  Also  these 
common  names  differ  in  different  countries;  that  is,  are  differ- 
ent in  different  languages.  The  animal  we  call  dog,  the  Ger- 
mans call  Hund,  the  French,  chien,  and  the  Italians,  cane. 
And  even  in  the  same  country  one  common  name  may  be 
applied  in  different  parts  of  it;  as  "quail"  which  means  one 
kind  of  bird  in  the  East,  another  kind  in  the  Mississippi  Valley, 
and  still  another  on  the  Pacific  Coast.  "Partridge"  has  still 
a  wider  divergence  of  application^  and  "minnow"  refers  to 
nearly  as  many  different  fishes  as  the  localities  in  which  the 
word  is  used. 

Thus  if  there  is  to  be  accurate  speaking  and  writing  about 
animals,  and  if  the  naturalists  of  different  countries  are  to  be 
able  to  use  names  that  are  understandable  to  all,  there  is 
necessary  some  system  of  naming  animals  other  than  the  popu- 
lar one  of  vernacular  names.  This  system  is  that  of  the  so- 
called  "scientific  names,"  or  two- word  names  in  Latin  or 
Greek,  devised  and  successfully  established  by  Linnaeus.  It 
is  a  system  which  has  given  rise  to  much  popular  fun-making 
and  no  little  scientific  discussion  and  dispute,  but  whose  use- 
fulness is  so  real  and  whose  principles  are  so  sound  that  it  will 
likely  never  be  given  up. 

The  names  used  in  it  are  all  Latin  or  Greek  simply  because 
these  classic  languages  are  taught  in  the  schools  and  colleges 
of  almost  all  the  countries  of  the  world,  and  are  thus  intelligible 
and  familiar  to  naturalists  of  all  nationalities.  In  the  older 
days,  indeed,  all  the  scientific  books,  the  descriptions  and 
accounts  of  animals  and  plants,  were  written  in  Latin,  and  now 


THE  CLASSIFICATION  OF  ANIMALS  51 

most  of  the  technical  words  used  in  naming  the  parts  of  animals 
and  plants  are  Latin.  So  that  Latin  may  be  called  the  language 
of  science.  For  most  of  the  groups  of  animals  we  have  English 
names  as  well  as  Greek  or  Latin  ones  and  when  talking  with  an 
English-speaking  person  we  can  use  these  names.  But  when 
scientific  men  write  of  animals  they  use  the  names  which  have 
been  agreed  on  by  naturalists  of  all  nationalities  and  which 
are  understood  by  all  of  these  naturalists.  These  Latin  and 
Greek  names  of  animals,  laughed  at  by  non-scientific  persons 
as  "jaw-breakers,"  are  really  a  great  convenience,  and  save 
much  circumlocution  and  misunderstanding. 

Zoological  Classification  and  Nomenclature. — In  any  dis- 
cussion of  the  nomenclature  of  zoological  classification  it  is 
first  of  all  necessary  to  distinguish  between  the  few  names 
used  as  common  nouns,  such  as  species,  genus,  family,  order, 
etc.,  which  denote  the  different  kinds  of  groups  into  which 
animals  are  divided,  and  the  host  of  proper  noun  names  which 
are  applied  to  the  many  groups  of  each  kind  which  have  been 
established  by  students  of  systematic  zoology. 

A  single  kind  of  animal,  as  a  house-fly,  a  robin  or  a  coyote, 
is  called  a  species  of  animal.  Coyotes,  dogs  and  gray  wolves 
are  different  species  much  alike.  They  are  grouped  together 
with  some  other  kinds  of  wolves  and  dog-like  animals  to  form 
a  group  called  a  genus.  The  robin  belongs  to  a  genus  which 
includes  one  or  two  other  robin-like  species  of  birds  and  the 
house-fly  to  a  genus  which  includes  several  other  house-fly 
species  of  insects.  Each  of  these  genera  has  a  proper  name, 
which  distinguishes  it  from  all  other  genera,  and  for  that  matter 
from  all  other  groups  of  animals,  because  a  genus  name  is 
never  used  for  more  than  one  group  of  animals.  The  dog- 
coyote-wolf  genus  is  called  Canis,  the  robin  genus,  Merula, 
and  the  house-fly  genus,  Musca. 

Each  species  belonging  to  these  genera  also  has  a  specific 
proper  name,  the  dog's  species  name  being  familiaris,  the 
coyote's  latrans,  the  gray  wolf's  occidentalis,  the  robin's  migra- 
loria,  and  the  house-fly's  domestica.  But  because  of  the 
enormous  number  of  kinds  of  animals  we  do  not  try  to  have 
a  separate  single  word  name  for  each  species,  but  always  com- 


52      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

bine  the  species  name  word,  which  may  be  used  repeatedly, 
that  is,  used  for  several  different  species,  with  the  name  of 
the  genus  to  which  the  species  belongs,  and  thus  make  a  two- 
word  name,  or  "binomial,"  for  each  animal  kind.  These 
two-word  names  distinguish  the  species  unmistakably  from 
each  other  because  although  the  same  word,  familiaris,  may 
be  used  for  several  or  even  many  different  species  it  is  never 
used  for  more  than  one  species  in  any  given  genus,  and  the 
genus  name  is  never  used  for  more  than  a  single  genus.  So 
that  Canis  familiaris,  the  scientific  two- word  name  for  the  dog 
species,  unmistakably  distinguishes  the  dog  by  name  from 
all  the  other  half  million  species  of  animals  we  know.  There 
might  be  a  Merula  familiaris,  or  a  Musca  familiaris  in  the  list, 
but  not  a  second  Canis  familiaris.  You  will  have  noticed 
that  we  have  capitalized  the  first  or  genus  word  in  the  two- 
word  scientific  name  of  the  dog,  but  not  the  second  or  species 
word.  And  this  is  the  rule  in  zoological  nomenclature.  Even 
if  the  species  word  is  derived  from  a  proper  name,  as  is  often 
the  case,  it  is  not  capitalized.  The  botanists  do  not  adhere  to 
this  rule,  so  that  they  might  write  Canis  Browni,  if  Canis  were 
the  genus  name  of  a  plant  and  Browni  the  species  name. 

Just  as  there  are  often  several  and  sometimes  many  species 
sufficiently  alike,  or  better,  closely  enough  related,  to  be 
grouped  together  into  one  genus,  so  there  are  usually  several 
or  many  genera  related  closely  enough  to  be  brought  together 
into  a  group  of  a  higher  or  more  comprehensive  degree.  There 
are,  for  example,  other  genera  of  animals  showing  unmistakable 
affinities,  by  their  resemblances  of  structure,  with  the  dog  and 
wolf  genus  Canis.  Such  for  example  are  the  genera  Vulpes 
and  Urocyon  which  include  various  species  of  foxes.  These 
related  genera  are  then  grouped  together  to  form  a  family;  in 
this  case  the  family  Canidce.  Note  that  the  proper  name  of 
this  family  is  made  by  adding  idee  to  the  stem  part  of  the  name 
of  one  of  the  genera  in  it.  That  is,  the  name  of  an  important 
genus  in  the  family  is  taken  in  the  genitive  case  and  pluralized 
in  order  to  make  the  family  name.  And  this  is  a  general  rule 
in  zoological  nomenclature. 

Related    families    are   grouped    together    to    form    orders. 


THE  CLASSIFICATION  OF  ANIMALS  53 

Plainly  related  to  the  Canidce,  for  example,  are  the  Felidce,  or 
cats  and  cat-like  animals,  the  Ursidce,  or  bears,  Mustelidce  or 
weasels,  and  some  other  families  all  of  whose  members  are 
carnivorous  in  habit  and  have  teeth,  feet,  and  other  parts 
specially  modified  in  connection  with  this  habit.  All  of  these 
families  then  are  grouped  together  to  form  the  order  Carnivora. 
All  the  families  of  hoofed  animals,  as  the  Equidce  or  horses,  the 
Bovidce  or  cattle,  the  Cervidce  or  various  deer  kinds,  and  other 
similar  families,  compose  the  order  Ungulata.  But  all  the 
animals  of  both  Carnivora  and  Ungulata  as  well  as  of  a  number 
of  other  orders  agree  in  possessing  certain  important  common 
characteristics  of  structure  and  physiology,  which  undoubtedly 
indicate  a  certain  relationship.  And  so  they  are  grouped  to- 
gether to  form  a  class.  The  particular  class  comprising  the 
orders  just  spoken  of  is  named  the  Mammalia,  from  the  posses- 
sion by  all  of  its  members  of  milk  glands  for  producing  milk 
for  their  young. 

Finally  there  is  a  plain  relationship  among  the  class  Mam- 
malia or  mammals,  and  the  class  Aves,  or  birds,  the  class 
Reptilia,  or  reptiles,  the  class  Amphibia,  or  batrachians  and  the 
class  Pisces  or  fishes.  They  are  all  back-boned  animals,  while 
other  animals  are  not.  They  may  be  grouped  together  into 
a  single  large  group  called  a  branch.  The  name  of  this  branch 
is  the  Chordata.  There  are  eleven  other  branches  in  the  animal 
kingdom,  all  of  which  are  named  and  divided  into  their  classes 
in  the  table  on  pages  55  to  57. 

The  branches  are  the  largest  groups  used  in  the  classi- 
fication of  animals,  so  that  if  we  should  now  tabulate  the 
scientific  classification  of  our  dog  we  should  find  it  to  belong 
to  the 

kingdom  Animalia 
branch  Chordata 
class  Mammalia 

order  Carnivora 
family  Canidae 
genus  Canis 

species  familiaris. 

Its  scientific  name  is,  however,  simply  Canis  familiaris,  which 
indicates,  to  a  zoologist,  the  whole  classification  of  the  dog. 


54      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Because  as  there  is  but  one  animal  genus  named  Cams  and 
that  is  a  member  of  the  family  Canidae,  which  in  turn  is  a 
member  of  the  order  Carnivora,  which  is  a  member  of  the 
class  Mammalia,  which,  finally,  belongs  to  the  great  branch 
Chordata,  we  have  indicated  all  the  superior  groups  by  naming 
the  generic  one  only,  and  have  pointed  out  what  particular 
species  of  that  genus  wre  are  referring  to,  when  we  simply 
say  or  write  Canis  familiaris. 

There  are  many  rules  of  custom  which  zoologists  try  to 
follow  in  deciding  on  names  for  new  kinds  and  groups  of  ani- 
mals, but  they  are  too  many  and  too  technical  to  discuss  here. 
However  it  is  worth  while  to  point  out  that  while  the  scientific 
name  of  an  animal  may  be  more  or  less  descriptive  by  the 
meaning  of  its  genus  and  species  words,  it  is  not  necessarily 
so.  Canis  familiaris  is,  translated,  the  common  dog;  Canis 
latrans,  the  barking  dog;  and  Canis  occidenialis  the  western  dog, 
which  are  all  therefore  names  of  descriptive  nature.  But 
there  might  be  a  wolf  named  Canis  smithi,  which  would  not 
describe  it  at  all.  The  name  however  would  be  a  perfectly 
proper  scientific  name.  There  are  indeed  hundreds  of  scien- 
tific names  which  have  no  or  almost  no  descriptive  significance 
at  all;  and  some  that  are  even  wrongly  descriptive.  For  ex- 
ample a  Russian  naturalist  might  find  in  the  wilds  of  Siberia 
a  new  kind  of  wolf,  larger  than  any  other  kind  known.  He 
might  name  it  therefore,  descriptively,  Canis  maximtis,  the 
largest  wolf.  In  the  next  year  an  American  naturalist  might 
find  a  still  larger  species  in  the  heart  of  Alaska.  But  the  name 
Canis  maximus  would  always  be  used  for  the  smaller  Siber- 
ian wolf,  because  the  scientific  name  is  primarily  a  symbol, 
an  arbitrary  name,  and  not  a  description.  And  also  the  ad- 
vantage of  having  the  first  name  applied  to  a  species  retained 
for  all  time  is  very  great.  The  stability  of  the  system  and  its 
convenience  depend  largely  on  the  custom  of  not  changing  the 
names  unless  absolutely  necessary  because  of  some  original 
mistake  in  assigning  the  species  to  a  wrong  genus,  or  the 
necessity  of  dividing  too  bulky  genera  into  smaller  ones. 

Branches  and  Classes  of  Animals.— The  following  table  gives 
the  names  and  arrangement  of  all  the  branches  and  classes  of 


THE  CLASSIFICATION  OF  ANIMALS  55 

the  animal  kingdom.     No  attempt  should  be  made  now  to 
memorize  this  table. 

ANIMAL  KINGDOM 

BRANCH  I.  PROTOZO'A  (one-celled  animals) 

Class        I.  Rhizfip'oda    (amoeba,  Heliozoa,  Radiolaria,  Foraminif- 

era,  et  al.). 

Class       II.  Mycetozo'a  (slime-moulds). 
Class     III.  Mastigoph'ora   (whip-bearers,  Euglena,   trypanosomes, 

Spirochata,  et  al.). 
Class      IV.  Spdrozo'a    (parasitic    Protozoa    such    as    Plasmodium 

which  causes  malaria,  Babesia  which  causes  Texas 

fever  of  cattle,  et  al.). 
Class       V.  Infuso'ria  (mostly  free-swimming  Protozoa  provided 

with  cilia,  Paramoecium,  Vorticella,  et  ah). 

BRANCH  II.  PORIF'ERA  (sponges) 
Class        I.  For  if  era  (sponges). 

BRANCH  III.  CCELEN'TERA'TA  (se-len-te-ra'-ta) 

(Aquatic,  mostly  marine,  radially  symmetrical  ani- 
mals having  a  combined  body  and  stomach  cavity) 
Class        I.  Hydrozo'a  (fresh  water  hydra,  marine  hydroids,  many 

of  the  small  jelly-fish,  a  few  stony  corals,  et  al.). 
Class       II.  Scyphdzo'a  (sl-fo-zo'-a)  (most  of  the  large  jelly-fishes). 
Class     III.  Actlnozo'a  (sea-anemones;  most  of  the  corals,  et   al.). 
Class     IV.  CtSndph'ora   (ten-oph'-o-ra)  (the  comb-  jellies,  or  sea- 
walnuts). 

BRANCH  IV.  PLATYHELMIN'THES  (flat-worms) 

Class  I.  Turbellar'ia  (planarians,  et  al.). 
Class  II.  Tremato'da  (liver-flukes,  et  al.). 
Class  III.  Cesto'da  (tape- worms). 

BRANCH  V.  NEMATHELMlN'THES  (round-worms) 

Class        I.  NSmato'da  (trichina,  hookworms,  et  al.). 

Class       II.  NematomSr'pha  (horse-hair  snakes,  or  cabbage- snakes, 

et  al.). 

Class     III.  Acanthoceph'ala  (thorn-headed  worms). 
Class     IV.  Ch(zt8g'natha  (ke-tog'-na-tha)  (arrow- worms). 


56      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

BRANCH  VI.  TROCHELMIN'THES  (wheel-worms) 
Class        I.  Rotifer  a  (wheel  animalcules). 

BRANCH  VII.  M(3LLUSCOI'DA 

(small  animals  which  are  more  or  less  mollusc-like) 

Class        I.  Pdlyzo'a  (moss-animals). 

Class       II.  Phord'nida  (worm-like  animals  living  in  sand). 
Class     III.  Br&chiop' oda  (lamp-shells,   small  marine  animals  with 
a  bivalve  shell). 

BRANCH  VIII.  ECHINODER'MATA 

(radially  symmetrical,  marine  animals  with  a  rough 
or  spiny  skin) 

Class  I.  Aster oi'dea  (starfishes). 

Class  II.  Ophiuroi'dea  (brittle-stars). 

Class  III.  Echinoi'dea  (sea-urchins). 

Class  IV.  Hdlothur  oi'dea  (sea-cucumbers). 

Class  V.  Crlnoi'dea  (sea-lilies,  or  feather-stars). 

BRANCH  IX.  ANNEL'IDA  (segmented  worms) 

Class        I.  Archiannffl ida  (marine  worms  living  in  the  sand). 

Class       II.  Chcetdp'oda  (earthworms,  Nereis,  et  al.). 

Class  III.  Gephyre'a  (jef-e-re'-a)  (marine,  worms  of  uncertain 
relationship,  with  little  or  no  traces  of  segmenta- 
tion in  the  adult). 

Class      IV.  Hirudlriea    (leeches) 

BRANCH  X.  ARTHR^P'ODA 

(animals  with  the  body  more  or  less  distinctly  seg- 
mented and  with  jointed  appendages) 

Class        I.  Crustd'cea  (crayfish,  lobsters,    crabs,  shrimps,  et  al.). 

Class  II.  Onychdph'ora  (slime-slugs). 

Class  III.  Myri&p'oda  (myriapods,  centipedes,  et  al.). 

Class  IV.  Insec'ta  (insects). 

Class       V.  Arach'nida  (scorpions,  spiders,  mites  and  ticks). 

BRANCH  XI.  M6LLUS'CA 

(bilaterally  symmetrical,  unsegmented  animals,  most 
of  which  have  shells) 

Class        I.  AmpMneu'ra  (chitons,  et  al.). 

Class       II.  Gastrdp'oda  (snails,  slugs,  et  al.). 

Class  III.  Scaphop'oda  (tooth-shells). 

Class  IV.  Pelcc^p' oda  (clams,  mussels,  oysters,  scallops,  et  al.). 

Class       V.  Cephaldp'oda  (squids,  octopods  and  nautili). 


THE  CLASSIFICATION  OF  ANIMALS 


57 


BRANCH   XII.    CHORD  A 'TA 

(animals  that  have  a  notochord  at  some  stage  of  their 
development) 


Class  I, 

Class  II. 

Class  III 

Class  IV 

Class  V. 

Class  VI. 

Class  VII. 
Class  VIII. 

Class  IX. 


Adelochor'da  (balanoglossids,  et  al.). 

Urochor'da  (ascidians,  et  al.). 

Leptocard'ii  (lancelets). 

Cyclostdm' ata  (lampreys  and  hagfishes). 

Pisces  (pis-sez)  (fishes). 

Amphib'ia    (frogs,    toads,    salamanders,    water-dogs, 

et  al.). 

ReptU'ia  (snakes,  lizards,  turtles,  alligators,  et  al.). 
A'ves  (birds). 
M&mmdl'ia  (mammals). 


CHAPTER  IX 
SPONGES,  AND  SPONGE  FISHING 

The  sponges  are  fixed,  aquatic,  plant-like  animals  living 
mostly  in  salt  water.  They  are  regarded  as  representing  the 
simplest  type  of  Metozoan  body  structure  and  cell  specializa- 
tion, and  are  classified  as  a  branch  of  the  animal  kingdom 
called  Porifera.  The  body  of  the  simplest  sponges  is  vase- 
shaped  or  cylindrical  with  the  base  attached  to  a  rock  or  shell 
or  other  firm  substance.  At  the  free  end  there  is  an  opening 
that  leads  down  into  the  central  cavity.  The  walls  surround- 
ing this  cavity  are  perforated  by  numerous  openings  or  canals 
through  which  the  water  flows. 

Few  sponges  are  of  this  simple  vase-like  appearance,  how- 
ever. Most  of  them  are  unsymmetrical,  and  cling  close  to 
the  surface  on  which  they  grow,  or  form  low  compact  bushy 
bodies  looking  much  more  like  plants  than  like  animals. 

Sponges  belonging  to  the  genus  Grantia  are  convenient  types 
for  study.  They  live  in  salt  water  and  may  be1  obtained  at 
many  points  on  the  Atlantic  or  Pacific  Coasts  on  rocks, 
shells  or  other  objects  below  low  water  line.  They  are  sub- 
cylindrical  in  form,  attached  at  the  base,  and  with  a  rather 
large  opening,  the  exhalant  opening,  or  osculum,  at  the  free  end. 
All  over  the  sides  are  numerous  small  openings  leading  into  the 
inhalant  canals  which  extend  almost  to  the  inner  or  gastric 
cavity  or  cloaca.  Opening  into  the  cloaca  and  extending 
almost  to  the  outer  wall  are  other  canals,  the  radial  canals. 
The  inhalant  and  radial  canals  run  side  by  side  and  communi- 
cate with  each  other  by  means  of  very  small  openings.  The 
cells  lining  the  radial  canal  are  furnished  with  long  lashes,  or 
flagella,  the  lashing  of  which  sets  up  currents  of  water  which 

1  Inland  schools  can  obtain  specimens  preserved  in  alcohol  or  formalin 
from  dealers  in  natural  history  supplies. 

58 


SPONGES,  AND  SPONGE  FISHING  59 

passes  in  through  the  inhalant  canals  and  through  the  small 
openings  into  the  radial  canals  on  into  the  cloaca  and  out 
through  the  exhalant  opening  at  the  free  end  of  the  sponge. 
The  cells  lining  the  radial  canals  and  the  cloaca  take  up  and 
digest  particles  of  food  that  are  brought  in  by  the  currents  of 
water.  Some  of  this  digested  food  is  passed  by  osmosis  to  the 
adjacent  cells  which  do  not  take  up  any  food.  Here  we  see  a 
simple  step  in  physiological  division  of  labor.  The  outer  cells, 


FIG.  13. — A  group  of  vase-shaped  sponges,  Lencandra  apicalis.     (Natural 

size.) 

which  compose  the  ectoderm,  or  outer  skin,  serve  to  protect 
the  animal,  while  the  inner  cells,  which  make  up  the  endoderm, 
digest  the  food  and  feed  the  other  members  of  the  colony. 
The  currents  that  bring  the  food  also  bring  fresh  oxygen  in  the 
water.  Some  of  this  is  taken  up  by  the  cells,  while  the  carbon 
dioxide  and  other  wast^products  that  they  excrete  are  carried 
away  by  the  same  currents. 

Between  the  ectoderm  and  the  endoderm,  and  pierced  by 


60      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  inhalant  and  radial  canals,  is  the  soft  gelatinous-like 
layer,  the  mesoderm,  that  is  composed  of  various  kinds  of  cells. 
Some  of  these  are  concerned  in  the  formation  of  the  spicules 
that  make  up  the  framework,  some  are  concerned  with  diges- 
tion and  some  with  reproduction.  Two  or  three  kinds  of  spic- 
ules may  be  found  in  the  mesoderm  of  Grantia.  They  are 
composed  of  carbonate  of  lime,  and  are  very  brittle  when  dry. 
The  framework  of  the  commerical  sponges  is  composed  of 
exceedingly  fine  flexible  fibers  of  a  horny  substance  called 
spongin.  This  is  the  part  of  the  animal  that  we  commonly 
know  as  the  sponge  in  the  market. 

Grantia  reproduces  itself  in  two  different  ways.  Small  buds 
sometimes  appear  on  the  external  surface  of  the  body  which 
develop  into  small  individual  sponges.  These  gradually 
increase  in  size  and  finally  break  away  from  the  parent  and 
attach  themselves  to  some  other  substance.  In  the  more 
complex  sponges  these  buds  do  not  break  away,  but  remain 
attached  so  that  in  time  there  is  built  up  a  complex  sponge 
colony. 

Besides  this  method  of  reproducing  asexually,  that  is,  with- 
out the  union  of  two  kinds  of  germ  cells,  all  sponges  have  a 
mode  of  sexual  reproduction.  The  male,  or  sperm,  cells  and 
the  female,  or  egg,  cells  are  produced  in  the  same  individual. 
The  sperm  cells  when  ripe  are  cast  into  the  water  and  swim 
about  until  they  come  in  contact  with  egg  cells  which  they 
fertilize.  From  these  fertilized  egg  cells  sponge  embryos 
develop  which,  after  they  have  reached  a  certain  stage,  swim 
away  by  means  of  many  cilia  which  cover  their  bodies  and 
finally  attach  themselves  to  some  substance  where  they  remain 
the  rest  of  their  lives. 

Sponges  of  Commerce. — All  sponges  have  the  same  general 
type  of  structure  but  most  of  them  branch  extensively  and 
form  immense  colonies  with  innumerable  canals  and  cavities 
making  altogether  a  complicated  network.  The  sponges  that 
we  use  are  really  only  the  skeletons  of  some  of  these  great 
colonies  with  all  of  the  soft  parts  dried  or  squeezed  or  washed 
out.  Bleaching  powders  or  acids  are  sometimes  used  to 
lighten  the  color,  but  they  are  apt  to  injure  the  fibers.  The 


SPONGES,  AND  SPONGE  FISHING 


61 


best  sponges  come  from  the  Mediterranean.  This  region 
annually  produces  about  $2,000,000  worth  of  sponges,  which 
is  more  than  half  the  value  of  the  product  of  the  sponge 
fisheries  of  the  world.  Some  sponges  come  from  the  Red 
Sea,  others  from  the  Bahama  Islands,  West  Indies,  the  west 
coast  of  Florida  and  other  places.  The  annual  output  from 
the  Florida  sponge  fisheries  is  valued  at  between  $500,000  and 
$600,000.  The  commercial  sponges  do  not  live  in  very  deep 


FIG.  14. — A  common  bath  sponge.     (Reduced.) 

water,  being  usually  found  not  deeper  than  200  feet.  In  shal- 
low water  they  are  dragged  from  the  rocks  by  men  in  boats 
who  use  long  poles  with  hooks  on  the  ends.  Those  growing  in 
deeper  water  are  dredged  up  or  brought  up  by  divers. 

Many  of  the  best  sponge-fishing  grounds  have  suffered  very 
severely  from  destructive  methods  of  fishing  and  efforts  are 
now  being  made  to  protect  these  beds  and  to  stock  others. 
Several  methods  of  sponge  culture  have  been  tried,  most  of 


62      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

them  with  little  or  no  success.  The  United  States  Bureau 
of  Fisheries  has  found  a  method  that  it  believes  to  be  practi- 
cable. Live  sponges  are  cut  into  small  pieces  which  are 
fastened  on  some  firm  support  and  placed  in  suitable  places. 
In  from  four  to  six  years  these  fragments  grow  to  a  good 
marketable  size. 

Boring  Sponges. — Among  the  most  interesting  and  impor- 
tant of  the  sponges  are  the  boring  sponges  which  live  on  shells, 
spreading  over  the  surface  at  first  but  eventually  penetrating 
the  shell  in  every  direction,  completely  honeycombing  it,  and 
causing  it  to  break  up.  They  thus  help  to  dispose  of  the  shells 
of  dead  molluscs  which  would  otherwise  accumulate  in  vast 
quantities.  They  also  attack  shells  in  which  the  animals  are 
still  living  and  by  boring  through  the  shell  greatly  irritate  the 
host  which  must  constantly  secrete  new  shell  to  close  up  the 
holes  made  by  the  intruder.  These  boring  sponges  are  often 
serious  pests  in  the  oyster  beds.  The  pearl-shell  fishermen 
sometimes  find  some  of  their  largest  and  otherwise  finest  shells 
completely  ruined  by  the  work  of  some  of  them. 

Classification. — There  is  only  one  class  belonging  to  the 
branch  Porifera  (L.  porus,  pore;  fero,  to  bear)  and  that,  too, 
is  called  Porifera.  It  is  divided  into  two  sub-classes,  the 
Calcarea,  including  those  sponges  with  a  skeleton  of  calcareous 
spicules,  and  the  Non-calcarea,  with  the  skeleton  either  absent 
or  composed  of  spong  in  fibers  or  of  siliceous  spicules.  Grantia 
is  an  example  of  the  sub-class  Calcarea;  the  commercial 
sponges,  the  boring  sponges,  and  indeed  most  of  the  others, 
belong  to  the  Non-calcarea. 


CHAPTER  X 
CORALS,  SEA-ANEMONES  AND  JELLY-FISHES 

Like  the  sponges,  most  of  the  polyps,  and  jelly-fishes,  com- 
posing the  branch  Coelenterata  (Gr.  koilos,  hollow;  enter  on, 
intestine)  are  found  in  the  sea.  Those  who  live  near  the  sea- 


FIG.  15. — Sea-anemones.     The  middle  specimen  expanded  and  feed- 
ing; lower  specimens  partly  or  wholly  contracted  and  with  disk  closed. 

shore  are  familiar  with  the  many-colored,  flower-like  sea- 
anemones  that  cover  the  rocks  in  shallow  water,  and  with  the 
clear  transparent  medusae  or  jelly-fishes,  which  truly  look 
like  masses  of  animated  translucent  jelly.  Less  familiar  are 

63 


64      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  little  tree-like  hydroids  that  are  found  on  the  submerged 
rocks  or  shells  along  the  shore  at  all  depths.  These  little 
animals  look  so  plant-like  that  they  are  often  called  zoo- 
phytes, or  plant-animals,  a  name  that  is  also  applied  to  other 
polyps.  Many  of  them  however  live  a  part  of  their  lives  as 
active,  free-swimming  forms  before  they  settle  down  to  be- 
come attached  to  the  places  where  they  are  to  remain.  In 
the  shallow  waters  of  all  tropical  seas  the  coral  polyps  grow  in 
such  numbers  that  their  myriad  skeletons  form  whole  groups 
of  little  islands  and  great  projecting  barrier  reefs  that  may 
reach  for  miles  along  the  shores.  The  great  barrier  reef  off 
the  north  shore  of  Australia  is  more  than  a  thousand  miles 
long.  Only  a  few  of  the  polyps  live  in  fresh  water.  Hydra, 
which  is  found  in  nearly  all  fresh  water  ponds  or  streams,  is 
the  most  familiar  example,  and  has  already  been  studied. 

Hydroids  and  Jelly-fishes. — In  each  of  the  four  groups,  or 
classes,  into  which  the  polyps  and  jelly-fishes  are  divided  there 
are  many  modifications  of  the  simple  type  plan  presented  by 
Hydra.  If  the  buds  that  develop  on  Hydra  should  remain 
attached  and  continue  to  grow  and  in  turn  produce  other  buds, 
there  would  soon  be  developed  a  tree-like  colony  with  a  Hydra- 
like  animal  at  the  end  of  each  branch.  Some  marine  animals 
are  developed  in  just  this  way,  and  are  known  as  hydroids.  The 
class  Hydrozoa  (Gr.  hydor,  water;  zoon,  animal)  to  which  these 
belong  includes  the  Hydra  and  other  Hydra-like  animals.  The 
Hydrozoan  colonies  may  be  made  up  of  two  kinds  of  in- 
dividuals, or  zooids.  One  kind,  known  as  the  nutritive  zooids, 
or  polyps,  retains  much  of  the  general  appearance  of  the 
Hydra;  the  other  kind,  known  as  the  reproductive  zooids,  or 
medusae,  develop  into  quite  different  looking  animals.  The 
medusae  are  produced  by  budding  off  from  the  bases  of  the 
polyps.  They  are  umbrella-shaped,  jelly-like  masses  and  are 
commonly  known  as  jelly-fishes.  After  budding  off  from  the 
polyps  they  float  and  swim  in  the  water  for  some  time  and 
finally  produce  egg  cells  and  sperm  cells.  From  each  fer- 
tilized egg  a  new  individual  develops.  This  new  individual 
is  at  first  an  active  free-swimming  larva,  called  planula,  which 
does  not  resemble  either  a  medusa  or  a  polyp.  After  a  while 


CORALS,  SEA-ANEMONES  AND  JELLY-FISHES  65 

it  settles  down,  becomes  fixed,  and  develops  into  a  polyp. 
Thus  a  polyp  may  produce  a  medusa  or  jelly-fish  which,  how- 
ever, produces  not  a  new  jelly-fish,  but  a  polyp.  This  is  called 
an  alternation  of  generations,  and  is  not  an  uncommon  phenom- 
enon among  the  lower  animals.  It  results  from  such  an  al- 
ternation of  generations  that  a  single  species  of  animal  may 
have  two  distinct  forms.  This  having  two  different  forms  is 


FIG.  1 6. — A  jelly-fish,  or  medusa,  Gonionema  vertens,  eating  two  small 
fishes.     (From  specimen  from  Atlantic  Coast.) 

called  dimorphism.  Sometimes,  indeed,  a  species  may  appear 
in  more  than  two  different  forms;  such  a  condition  is  called 
polymorphism. 

The  Portugese  man-of-war,  common  in  tropical  seas,  is  a 
representative  of  another  group  of  this  class.  It  appears 
as  a  delicate  bladder-like  float,  brilliant  blue  or  orange  in 
color,  usually  about  six  inches  long,  and  bearing  on  its  upper 


66      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

surface,  which  projects  above  the  water,  a  raised  parti-colored 
crest,  and  on  its  under  surface  a  tangle  of  various  appendages, 
some  thread-like  and  others  in  grape-like  clusters  of  little 
bell-  or  pear-shaped  bodies.  Each  of  these  parts  is  a  peculiarly 
modified  polyp-  or  medusa-zooid,  produced  from  budding 
from  an  original  central  zooid.  Many  other  kinds  of  colonial 
jelly-fishes  occur  which  show  similar  differences  among  the 
different  members  of  the  colony.  Some  individuals  enable 
it  to  move  through  the  water,  some  protect  the  colony,  others 
procure  or  digest  food  and  still  others  are  modified  into  re- 
productive organs.  The  whole  colony,  or  compound  animal, 
floats  or  swims  at  the  surface  of  the  water  and  performs  all 
the  necessary  functions  of  life  as  a  single  animal  composed  of 
organs  might. 

Most  of  the  common  large  jelly-fishes  belong  to  a  second 
group  (class  Scyphozoa:  Gr.  skyphos,  cup;  zoon,  animal).  They 
often  occur  in  great  numbers  on  the  surface  of  the  ocean. 
Others  live  in  deeper  waters,  a  few  having  been  dredged  up 
from  depths  of  even  a  mile  below  the  surface.  The  umbrella- 
shaped  bodies  vary  in  size  from  less  than  an  inch  to  more  than 
six  feet  in  diameter.  From  the  underside  of  the  central  part 
of  the  body  hangs  a  mass  of  long  tentacles  which  are  provided 
with  stinging-threads.  The  small  animals  that  become  en- 
tangled in  these  tentacles,  which  sometimes  reach  a  length 
of  more  than  100  feet,  are  stung  by  the  stinging-threads  and 
serve  as  food  for  the  jelly-fish.  The  body  substance  of  some 
jelly-fishes  is  more  than  99  per  cent,  sea-water.  Most  of 
them  are  nearly  transparent,  but  some  are  beautifully  colored 
and  many  are  phosphorescent. 

Sea-anemones  and  Corals.— The  most  familiar  examples  of 
the  polyps  and  jelly-fish  branch  of  animals  are  the  multi- 
colored sea-flowers,  or  sea-anemones,  found  along  all  ocean 
shores.  The  petal-like  tentacles,  that  surround  the  central 
mouth-opening  spread  wide  and  seize  and  thrust  into  the 
mouth  any  small  animals  that  may  walk  or  swim  into  this 
living  trap.  Less  common  are  the  beautiful  sea-pens,  sea- 
feathers  and  sea-fans  which  are  closely  related  to  the  sea- 


CORALS,  SEA-ANEMONES  AND  JELLY-FISHES  67 

anemones.     All  these  belong  to  the  class  Actinozoa  (Gr.  aktis, 
ray;  zoon  animal). 

To  this  class  belong  also  the  interesting  coral  polyps  that  are 
found  in  all  tropical  and  sub-tropical  seas.  The  individual 
coral  polyps  are  not  unlike  the  sea-anemones  in  general  ap- 
pearance and  structure,  but  they  usually  live  in  great  colonies, 
forming  large  irregular  or  branching  tree-like  masses.  As 
the  animals  grow  they  secrete  a  strong  skeleton  of  carbonate 
of  lime.  The  corals  with  which  most  of  us  are  familiar  are 


FIG.  17. — Branching    coral,    Acropora    muricata,    from  Samoa.     (Much 

reduced.) 

really  only  the  calcareous  skeletons  of  innumerable  little 
polyps.  The  living  coral  is  quite  different  in  appearance  from 
this  hard  stony  skeleton.  The  surface  is  often  soft  and  velvety, 
pink,  green,  yellow,  brown  or  purple,  and  covered  with  the 
small  waving  tentacles  of  the  numerous  little  polyp  individuals 
that  make  up  the  colony.  As  each  individual  polyp  dies  and 
leaves  its  skeleton  it  is  adding  its  small  mite  toward  the  for- 
mation of  the  great  coral  rocks  or  reefs  or  islands  charac- 
teristic of  the  tropical  seas.  Coral  polyps  usually  do  not  live 


68      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

more  than  fifteen  or  twenty  fathoms  below  the  surface  of  the 
water,  so  we  find  the  reefs  as  fringing  reefs  lying  attached  to 
some  shore  line,  or  as  barrier  reefs,  lying  a  little  further  out  and 
separated  from  the  land  by  an  intervening  lagoon.  Or  they 
may  be  in  the  condition  of  atolls,  which  make  up  groups  of  small 
coral  islands,  each  surrounding  a  more  or  less  circular  or  oval 
lagoon.  These  coral  islands  are  themselves  often  protected 
by  barrier  reefs.  The  foundations  upon  which  the  coral 
atolls  rest  are  probably  the  summits  of  submarine  mountains 
which  come  to  within  100  or  150  feet  of  the  surface.  On 
such  places  coral  polyps  and  many*  other  kinds  of  marine 
animals  and  plants  grow,  and  accretions  due  to  these  and 
other  substances  slowly  raise  the  bank  toward  the  surface 
of  the  water,  so  that  at  low  tide  the  tips  of  the  growing 
branches  of  the  coral  may  be  above  the  surface.  As  the 
coral  is  broken  and  ground  into  fine  bits  by  the  action  of  the 
waves  and  as  other  pieces  are  washed  higher  on  top  of  these, 
the  island  gradually  rises  above  the  level  of  the  tides.  The 
waves  continue  to  break  up  some  of  the  coral  into  fine 
particles,  that,  together  with  other  debris,  forms  a  little  cal- 
careous soil  in  which  may  germinate  the  seeds  carried  to  it  by 
birds  or  ocean  currents.  With  the  growth  and  decay  of  vege- 
table life  the  soil  gradually  becomes  more  fertile,  until  finally 
the  islands  may  become  covered  with  a  luxuriant  plant  growth 
which  in  turn  serves  as  the  home  of  many  insects  and  birds  and 
other  animals. 

There  are  over  200  kinds  of  coral  polyps  known.  Many 
kinds  are  used  for  ornaments  or  decoration.  The  red  coral, 
which  grows  chiefly  in  the  Mediterranean,  is  much  used  for 
jewelry.  The  rose-pink  coral  is  very  valuable,  some  of  the 
finest  kinds  selling  for  hundreds  of  dollars  an  ounce. 

To  the  class  Ctenophora  (Gr.  kteis,  comb;  phero,  bear) 
belong  a  few  peculiar  delicate,  transparent,  medusoid  jelly- 
fish, swimming  by  means  of  the  rhythmical  beating  of  several 
rows  of  vibratile  plates  and  not  by  means  of  the  motion  of 
the  bell  or  umbrella  as  in  the  case  of  other  jelly-fishes. 


CHAPTER  XI 

THE  LIVER-FLUKES,  TAPE- WORMS,  AND  OTHER 
PARASITIC   FLAT  WORMS 

The  Worms. — In  the  older  classifications  the  name  Vermes 
was  applied  to  a  large  group  of  worm-like  creatures  which 
resembled  each  other  in  some  respects,  but  as  these  animals 
came  to  be  better  known  it  was  found  that  some  were  not  at 
all  closely  related  to  others  and  it  became  necessary  to  divide 
the  group  into  five  smaller  groups  of  equal  rank,  the  flat  worms 
(Platyhelminthes,)  the  round  worms  (Nemathelminthes),  the 
rotifers  (Trochelminthes),  the  sea-mats  and  lamp-shells 
(Molluscoidea)  and  the  segmented  worms  (Annelida).  These 
all  differ  from  the  polyps  and  sponges  by  being  bilaterally 
symmetrical  and  in  having  three  well-developed  layers  of 
cells  in  the  body-wall,  the  mesoderm  being  well  developed. 
Usually,  also,  the  various  systems  of  organs  are  much  more 
complex,  and  the  individuals  do  not  form  colonies. 

The  first  group  (the  branch  Platyhelminthes;  Gr.  platus, 
broad,  helmins,  worm)  includes  the  liver-flukes,  tape-worms 
and  other  parasitic  flat-worms,  and  a  few  free  living  flat  worms 
that  live  in  fresh  water  or  salt  water,  or,  more  rarely,  on  land. 
They  are  usually  much  flattened  and  without  true  segmenta- 
tion, although  the  bodies  of  the  tape- worms  have  a  jointed 
appearance  owing  to  their  being  largely  made  up  of  a  string  of 
reproductive  units.  Many  of  the  parasites  have  very  com- 
plex life  histories  and  live  in  different  kinds  of  animals  while 
passing  through  their  successive  stages  of  development. 

Fresh-water  Planarians. — In  the  mud  at  the  bottom  of 
ponds  of  fresh  water  or  clinging  to  the  rocks  or  sticks  in 
such  places  are  often  found  small  flat  creatures  that  are  known 
as  planarians.  They  look  somewhat  like  small  leeches,  which 
belong  to  the  branch  Annelida,  but  may  be  distinguished 

69 


70      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

from  them  by  the  absence  of  rings  around  the  body.  These 
planarians  are  less  than  half  an  inch  long,  very  thin  and 
rather  broad.  On  the  upper  surface  near  the  front  is  a  pair 
of  pigmented  spots  which  are  probably  sensitive  to  light  and 
are  called  the  eyes.  The  mouth  is  on  the  under  surface  a 
little  behind  the  middle  of  the  body.  The  alimentary  canal 
is  composed  of  three  main  branches,  each  with  numerous 
small  side  branches.  One  main  branch  runs  forward  from 
the  mouth,  and  the  other  two  run  backward,  one  on  each  side 
of  the  body.  There  is  no  anal  opening,  and  the  alimentary 
canal  thus  forms  a  system  of  fine  branches  closed  at  the 
tips,  and  extending  all  through  the  body.  The  nervous 
system  is  composed  of  a  ganglion  or  brain  in  the  front  end  of 


FIG.  18. — A  fresh-water  planarian,  Planaria  sp.     (Eight  times  natural 
size;  from  a  living  specimen.) 

the  body  from  which  two  main  branches  extend  back  through- 
out its  whole  length.  From  these  main  longitudinal  branches 
arise  many  fine  lateral  branches. 

Many  beautiful  and  interesting  members  of  the  class 
Turbellaria — the  class  to  which  the  planarians  belong — are 
marine  and  a  few  are  found  in  moist  earth. 

Liver-flukes. — The  liver-flukes,  Fasciola  hepatica,  live  as 
parasites  in  the  liver  of  sheep  and  cattle,  especially  the  former. 
In  Europe  they  sometimes  kill  hundreds  of  thousands  of  sheep 
annually,  and  they  have  more  recently  become  of  some  import- 
ance in  the  United  States,  the  Pacific  and  the  Gulf  Coast 
regions  suffering  most.  They  are  interesting  not  only  on 
account  of  their  economic  importance  but  because  they  furnish 
a  good  example  of  a  Metazoan  parasite  that  requires  two 
different  kinds  of  hosts  in  which  to  complete  the  different  stages 


THE  LIVER-FLUKES,  TAPE- WORMS,  ETC.        71 


of  its  development.  The  adult  fluke,  which  occurs  in  the 
sheep's  liver,  has  a  flattened  leaf-like  body,  and  is  from  three- 
quarters  of  an  inch  to  more  in  length.  There  are  two  suckers 
on  the  ventral  side,  one  surrounding  the  mouth,  the  other 
nearer  the  anterior  end.  Their  presence  in  the  liver  produces 
a  disease  known  as  liver  rot  because  the  tissues  of  the  liver 
degenerate.  Affected  sheep  often  die. 

The  flukes  are  hermaphroditic,  and  each  individual  is  capable 
of  producing  about  five  hundred  thousand 
very  minute  eggs.  These  pass  through  the 
bile  ducts  of  the  host  into  the  alimentary 
canal  and  thence  with  the  excrement  to  the 
ground.  If  the  eggs  fall  on  dry  ground  they 
usually  perish,  but  if  they  fall  on  damp  herb- 
age or  in  water  there  hatch  from  them  small 
ciliated  larvae.  These  swim  about  in  the 
water  for  ten  or  twelve  hours,  and,  if  they 
do  not  happen  to  come  in  contact  with  a 
certain  kind  of  snail,  they  perish.  Those 
that  do  succeed  in  finding  a  snail  bore  their 
way  through  any  of  the  soft  parts  into  the 
body,  where  they  undergo  certain  changes, 
finally  forming  sporocysts  within  which  are 
developed  small  larvae  called  redice,  which  in 
turn  produce  other  rediae.  The  rediae  finally 
give  rise  to  certain  heart-shaped  bodies  each 
with  a  long  flexible  tail.  These  are  called  cer- 
carice,  and  in  this  shape  the  parasites  issue  from  the  snail 
host.  Soon  after  leaving  the  snail  the  cercariae  become  en- 
cysted and  within  the  cyst  further  changes  take  place,  the 
animal  becoming  more  like  a  minute  adult  fluke.  If  these 
cysts  are  swallowed  by  a  sheep  when  it  is  eating  grass  or 
drinking  water  where  they  occur,  the  cyst  is  dissolved  by  the 
digestive  juices  in  the  sheep's  stomach  and  the  young  flukes 
are  liberated.  They  soon  work  their  way  from  the  stomach 
to  the  duodenum  and  through  the  bile  duct  into  the  liver, 
where  they  develop  into  the  adult  flukes. 

It  will  be  seen  that  under  ordinary  conditions  there  is  little 


FIG.  19. — Liver- 
fluke,  Fasciola 
hepatica.  (Nearly 
twice  natural 
size.) 


72      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

chance  of  many  of  the  thousands  of  eggs  that  are  produced 
by  the  adult  fluke  ever  meeting  successfully  all  the  danger 
that  beset  their  path.  The  eggs  may  fail  to  reach  the  water;  or 
if  hatched  the  larvae  may  not  be  able  to  find  a  snail;  or  if  the 
snail  is  found  it  may  be  destroyed  before  they  have  completed 
their  transformations.  The  cercariae  are  always  in  danger  of 
being  eaten  by  aquatic  animals  while  in  the  water,  or  if  not 
eaten  after  they  form  their  cysts  the  particular  blade  of  grass 
to  which  they  are  attached  may  never  be  eaten  by  a  sheep. 
Yet  the  number  of  eggs  that  are  produced  is  so  great  that 
hosts  of  the  young  flukes  do  successfully  overcome  all  their 
difficulties  and  infect  so  many  sheep  that  they  become  an 
important  economic  factor  in  sheep-raising  in  many  regions. 

With  a  knowledge  of  the  life  history  of  the  parasite,  however, 
it  is  a  comparatively  easy  matter  to  prevent  the  infection  of  the 
sheep.  This  is  accomplished  by  keeping  them  away  from  land 
subject  to  overflow,  or  where  the  snails  occur  in  numbers. 
Springs  and  other  watering  places  are  particularly  dangerous 
when  there  are  many  snails  about  them. 

This  same  species  of  liver-fluke,  Fasciola  hepatica,  some- 
times occurs  in  cattle,  horses  and  other  domestic  animals 
and  even,  although  very  rarely,  in  man. 

Other  Flukes. — The  large  American  fluke,  Fasciola  magna, 
which  is  often  a  serious  pest  of  cattle  in  the  Southern  states, 
also  occurs  in  the  deer,  which  was  probably  its  original  host. 
The  life  history  has  not  yet  been  worked  out,  but  it  is  probably 
somewhat  similar  to  that  of  the  liver-fluke  of  sheep.  Another 
species  of  fluke  is  common  in  ducks,  and  many  other  animals 
may  be  more  or  less  seriously  affected  by  still  other  kinds. 
One  species  occurring  in  Egypt  is  a  dangerous  parasite  of  man, 
infesting  the  urinary  and  abdominal  blood-vessels  where  it 
causes  serious  inflammation.  The  infection  is  probably  from 
bad  water. 

Some  species  are  external  parasites  and  attach  themselves  to 
their  hosts  by  means  of  a  series  of  suckers.  One  kind  that 
attaches  itself  to  the  gills  and  fins  of  fresh-water  fishes  is 
viviparous,  that  is,  it  brings  forth  its  young  alive,  and  the 
embryo,  before  it  is  extruded,  itself  contains  another  embryo 


THE  LIVER-FLUKES,  TAPE- WORMS,  ETC.       73 

and  this  in  turn  still  another  embryo  so  that  three  generations 
of  embryos  are  present  one  within  the  other. 

Tape-worms. — The  tape-worms  are  the  most  common  and 
the  best  known  of  the  flat  worms.  There  are  many  species, 
the  adults  of  all  of  which  live  in  vertebrate  animals.  But  there  is 
almost  always  an  alternation  of  hosts  during  the  life  of  the 
parasite,  the  larval  tape-worm  living  in  one  animal  and  the 
adult  in  another.  In  the  larval  stage  the  tape-worms  may 
occur  in  various  parts  of  the  body  of  the  intermediate  host, 
but  the  adult  or  fully  developed  worm  always  occurs  in  the 
alimentary  canal  of  the  final  host.  Many  of  the  domestic 
animals  suffer  from  these  parasites.  At  least  ten  different 
species  of  tape-worms  have  been  found  in  the  dog,  the  inter- 
mediate hosts  including  rabbits,  sheep,  and  other  animals 
that  the  dog  may  feed  on.  Many  of  the  domestic  fowls  are 
infected  by  tape-worms,  whose  intermediate  hosts  are  insects 
or  small  aquatic  crustaceans,  like  Cyclops. 

Several  kinds  of  tape-worms  infest  man.  Tania  solium, 
whose  intermediate  host  is  the  pig,  may  serve  as  an  example 
of  the  group.  The  adult  worm  is  attached  to  the  inner  wall  of 
the  intestine  of  man  by  a  number  of  fine  hooks  with  which  the 
small  head  is  provided.  The  long,  ribbon-like,  symmetrical 
body  lies  free  in  the  alimentary  canal,  where  it  absorbs  the 
liquid  food  directly  through  its  thin  body-wall.  The  parasite 
has  neither  mouth  nor  alimentary  canal.  The  body  may 
reach  a  length  of  many  feet  and  be  composed  of  as  many  as 
850  segments,  or  proglottids.  Each  proglottid  produces  both 
sperm  cells  and  egg  cells,  and  as  these  become  mature  the 
posterior  proglottids  drop  off  one  by  one  and  pass  out  of  the 
alimentary  canal  with  the  excreta.  If  some  of  these  escaped 
proglottids  are  eaten  by  a  pig  the  embryos  issue  from  the  eggs, 
bore  through  the  walls  of  the  alimentary  canal  of  the  host,  and 
make  their  way  to  the  muscles,  where  they  increase  greatly  in 
size  and  develop  into  a  rounded  sac  filled  with  liquid.  In  this 
stage  they  are  large  enough  to  be  readily  seen,  and  the  infected 
spotted  meat  is  called  "measly  pork."  If  such  infected  pork 
is  eaten  by  man  without  being  cooked  sufficiently  to  kill  the 
parasites,  the  young  tape-worms  will  attach  themselves  to  the 


74      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


FIG.  20. — Some  segments  of  the  tape-worm,  Tania  saginata,  from  man. 
(About  natural  size.) 


THE  LIVER-FLUKES,  TAPE-WORMS,  ETC.       75 


walls  of  the  alimentary  canal  and  soon  develop  into  the 
many-jointed  adult.  Tape- worms  cause  much  trouble,  espe- 
cially to  children. 

It  is  probable  that  the  most  common  tape-worm  affecting 
man  in  the  United  States  is  one  that  passes  its  intermediate 
stage  in  cattle.  It  is  known  as  Tania  saginata,  and  is  much  like 
T.  solium,  but  the  head  is  depressed  instead  of  being  convex 
at  the  end,  and  the  hooks,  which  are  conspicuous  in  T.  solium, 
are  wanting  in  T.  saginata. 

It  is  plain  that  either  one  of  two  things  is  necessary  to 
prevent  infection;  all  meat  must  be  carefully  inspected  and 
any  that  is  "measly"  rejected,  or  it  must  all 
be  so  thoroughly  cooked  that  there  will  be 
no  chance  for  any  of  the  encysted  forms  to 
remain  alive. 


FIG.  21. — Head  of 


FIG.  22. — A  piece  of  a  muscle  of  the  ox,  with 
three  specimens  of  the  tape-worm,  Tcenia  saginata, 

ir*  £»rn-»irc  forl    oforro  ^AJof  ni-ol    oi^d«    o  f  f  Of  Ocf  OT-V*«l»/r    ^ 


tape-worm,  T  &nia       inree  specimens  01  cne  tape-worm,  i  wma-  saginaia, 
saginata.       (Highly      in  encysted  stage.     (Natural  size;  after  Osterberg.) 
m  a  g  n  i  fi  e  d  ;    after 
Wood.) 

If  a  child  or  an  older  person  becomes  infested  a  physician 
should  be  consulted,  as  many  of  the  vermifuges  that  are  often 
recommended  are  unsafe. 

A  serious  disease  of  sheep,  known  as  gid,  is  caused  by  the 
cysts,  or  "  bladder- worms, "  of  a  tape-worm,  Multiceps  multiceps 
(Ccenurus  cerebralis),  the  adult  stage  of  which  is  passed  in  the 
intestine  of  the  dog.  The  proglottids  pass  from  the  dog  in  the 
feces  and  the  eggs  are  released  and  splashed  on  the  grass  or 
washed  to  pools  where  the  sheep  drink  when  the  rains  come. 
When  the  eggs  are  taken  into  the  stomach  of  the  sheep  the 
embryo  is  released  and  makes  its  way  into  the  blood-vessels  and 


76      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

finally  to  the  central  nervous  system.     In  the  brain  it  grows 
rapidly  to  the  size  of  a  hazelnut,  or  larger,  the  sheep,  of  course, 


FIG.  23. — The  gid  parasite,  Multiceps  midticeps,  in  bladder-worm  stage 
from  brain  of  sheep.     (Much  reduced;  after  Hall.) 

suffering  from  the  movements  of  the  parasites  and  their 
presence  in  the  brain.  The  infected  sheep  usually  dies  and 
when  its  brain  infested  with  the  "bladder- worms"  is  eaten  by 


FIG.  24. — Adult  gid  tape-worm,  Midticeps  midticeps,  from  the  intestine  of 
the  dog.     (Natural  size;  after  Hall.) 

a  dog  or  some  other  carnivore  many  more  tape-worms  are 
produced  in  the  new  host. 


THE  LIVER-FLUKES,  TAPE-WORMS,  ETC.       77 

This  disease  has  been  a  serious  scourge  of  sheep  in  Europe 
for  centuries,  and  for  a  long  time  has  existed  in  Montana  where 
the  loss  is  at  least  $10,000  every  year.  The  number  of  the 
parasites  may  be  partially  controlled  by  keeping  only  a  few 
dogs  around  the  sheep  or  in  regions  where  they  are  feeding, 
and  by  keeping  these  dogs  free  from  tape-worms.  The  dogs 
should  never  be  allowed  to  feed  on  the  carcasses  of  the  sheep 
that  have  died  from  the  disease,  nor  is  it  well  to  let  them  feed 
on  the  heads  of  slaughtered  sheep  that  may  be  infected. 

Classification  of  the  Flat-worms. — The  Platyhelminthes  are 
divided  into  three  classes,  the  Turbellaria,  the  Trematoda, 
and  the  Cestoda.  Another  class,  the  Nemertea,  is  sometimes 
included  in  this  branch,  but  its  relation  is  doubtful.  Its 
members  are  of  no  economic  importance. 

The  Turbellaria  (L.  turbellce,  disturbance)  are  mostly  non- 
parasitic  and  have  the  epidermis  covered  with  cilia.  The 
fresh-water  planarians  are  examples. 

The  Trematoda  (Gr.  trema,  perforation;  eidos,  likeness) 
are  all  either  external  or  internal  parasites.  The  life  history, 
especially  of  the  internal  parasites,  is  often  very  complicated, 
as  we  have  seen  in  our  study  of  the  liver-flukes. 

The  Cestoda  (Gr.  kestos,  a  girdle,  eidos,  likeness)  are  all  in- 
ternal parasites  in  whose  life  history  there  occurs  a  tape- worm 
stage  in  a  vertebrate  host  and  a  bladder-worm  stage  in  a 
vertebrate  or  invertebrate  host.  The  tape- worms  of  man  and 
of  other  animals  are  examples  of  this  class. 

Parasites  and  Pearls. — After  calling  attention  to  so  much 
harm  that  these  lowly  parasites  may  cause  it  is  only  fair  that 
a  paragraph  should  be  given  to  pointing  out  how  a  few  of  them 
are  of  some  service  to  man.  For  a  long  time  it  has  been  known 
that  the  pearls  that  are  found  in  many  molluscs  are  secretions 
formed  about  foreign  particles  that  have  found  their  way  in- 
side the  shell.  It  is  now  known  that  the  larvae  of  several 
Trematode  and  Cestode  worms  are  the  objects  around  which 
some  of  the  finest  pearls  are  formed.  The  Trematode  larvae 
are  most  common  in  mussels,  while  the  Cestodes  are  found 
very  abundantly  in  the  pearl  oysters  of  Ceylon  and  other  parts 
of  the  world.  The  vertebrate  hosts  in  these  instances  are 


7 8   ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

usually  certain  fish  that  feed  on  the  molluscs.  In  these  the 
adult  parasite  lives,  and  some  of  the  young  embryos  that  are 
set  free  in  the  water  gain  access  to  the  gills,  liver  or  mantle  of 
the  molluscs.  Here  many  go  on  with  their  development  until 
the  mollusc  is  eaten  by  a  fish  and  the  life  cycle  is  begun  again. 
In  some  instances,  however,  the  irritation  due  to  the  presence 
of  the  parasite  causes  a  calcareous  secretion,  like  that  forming 
the  shell,  to  be  deposited  around  the  parasite.  This  forms  the 
nucleus  of  a  pearl  which  grows  by  additional  layers  being 
deposited  around  it,  the  luster  depending  on  the  kind  of  mollusc 
in  which  it  is  found.  "The  most  beautiful  pearl  is  only  the 
brilliant  sarcophagus  of  a  worm." 


CHAPTER  XII 


TRICHINA,    HOOKWORMS,    FILARIA,  AND    OTHER 
PARASITIC  ROUND-WORMS 


The  large  group  of  hair-like  or  thread-like  unseg- 
mented  worms,  constituting  the  branch  Nemathel- 
minthes  (Gr. nema,  thread;  helmins,  worm), includes 
certain  kinds  which  on  account  of  their  parasitic 
habits  are  of  very  great  economic  importance.  Per- 
haps the  most  familiar  examples  of  the  branch  are 
the  hair-worms,  or  horse-hair  snakes,  which  are  often 
found  in  watering  troughs  or  pools  of  water.  Be- 
cause of  their  remarkable  appearance  many  persons 
believe  them  to  be  horse-hairs  that  have  dropped 
into  water  and  changed  into  these  animals.  They 
really  come  mostly  from  the  bodies  of  insects  in 
which  they  pass  a  part  of  their  lives  as  parasites. 
The  vinegar-eel,  which  is  found  in  weak  vinegar  is 
another  common  example  of  the  group. 

Trichina. — The  dreaded  trichina,  Trichinella 
spiralis,  which  causes  the  disease  called  trichinosis, 
is  a  minute  round- worm  the  adults  of  which  live 
in  the  intestine  of  man,  pigs  and  other  animals. 
These  adults  produce  living  young  which  bore 
through  the  walls  of  the  intestine,  and  are  carried 
by  the  blood,  or  otherwise  make  their  way  to  the 
muscles,  where  they  form  little  cells  or  cysts  in 
which  they  lie.  The  presence  in  the  muscles  of 
thousands  or  millions  of  these  little  parasties  often 
causes  great  suffering,  sometimes  death  to  the  host. 
It  has  been  estimated  that  the  trichinosed  flesh  of 
a  human  subject  may  contain  100,000,000  of  these 
encysted  trichinae.  Before  further  development  of 

79 


FIG.  25. 
vinegar-eel, 
A  n  guillula 
sp.  (Great- 
1  y  magni- 
fied; from 
a  living 
specimen.) 


8o      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


the  worms  can  take  place  such  trichinosed  flesh  must  be  eaten 
by  another  animal  in  which  they  can  live.  Pigs  are  probably 
usually  infected  by  eating  dead  infected  rats  or  scraps  of  pork 
that  have  been  thrown  out  in  garbage.  Man  is  usually  in- 
fected by  eating  trichinosed  pork.  In  the  alimentary  canal  of 
the  new  host  the  trichinae  escape  from  the  cyst  and  after  be- 
coming sexually  mature  produce  the  young  which  migrate  to 
the  muscles  again. 

The  close  watch  that  the  government  inspectors  keep  over 
the  meats  that  go  out  from  all  the  great  packing  houses  makes 
the  dangers  from  all  parasites  of  this 
kind  very  much  less  than  it  used  to  be. 
But  the  meat  from  the  smaller  slaughter 
houses  is  usually  not  inspected  and  is 
always  a  source  of  danger.  No  pork, 
either  fresh  or  smoked,  should  be  used 
without  being  thoroughly  cooked  in 
order  that  any  trichinae  in  it  may  be 
killed. 

Eel -worms. — Belonging  to  the  genus 

pIG    26. Encapsuled    Ascaris    are    several    round- worms,   or 

trichinae  in  trunk  muscle    "eel- worms,"   some   of  which  are  very 

°-fiPig-  JGBatly  f ag~  common  and  of  considerable  economic 
nified;  after  Braun.; 

importance.  The  large-headed  thread- 
worm, Ascaris  megalocephala,  which  occurs  in  the  alimentary 
canal  of  the  horse,  reaches  a  length  of  from  eight  to  sixteen 
inches  and  may  be  as  thick  as  a  lead. pencil.  The  fertilized 
eggs  of  the  parasites  are  passed  from  the  body  of  the  host 
with  the  excreta,  and  probably  gain  entrance  to  a  new  host 
through  stagnant  water  or  by  a  horse  eating  grass  or  leaves  on 
which  the  eggs  occur. 

A  similar  but  somewhat  smaller  species,  Ascaris  lumbri- 
coides,  occurs  in  man  and  in  sheep  and  hogs.  In  children, 
particularly  in  tropical  regions,  these  parasites  may  occur  in 
large  numbers,  sometimes  from  one  to  ten  hundred  in  a 
single  individual.  In  such  cases  they  may  cause  nervous- 
ness, irritability,  hysteria  or  even  convulsions.  In  some  cases 


TRICHINA,  HOOKWORMS,  FILARIA,  ETC.       81 

the  parasites  may  emigrate  to  other  parts  of  the  host,  but 
ordinarily  they  remain  in  the  alimentary  tract. 

The  life  history  and  mode  of  infection  are  similar  to  those  of 
the  preceding  species.  The  eggs  may  be  washed  from  the 
feces  into  drinking  water,  or  they  may  become  dry  and  be  blown 
about  as  dust  or  become  attached  to  fruit  or  vegetables. 
Soon  after  they  reach  the  stomach  of  their  host  they  begin 
their  development.  Strong  vermifuges  are  necessary  to  re- 
move them,  but  such  medicines  should  be  used  only  under 
the  doctor's  advice. 

Still  another  species,  Ascaris  canis,  is  a  very  serious  pest  of 
dogs,  especially  puppies,  and  often  causes  serious  losses  to 
breeders  of  these  animals.  It  occurs  also  in  cats,  lynxes  and 
lions. 

The  stomach  worm  of  sheep,  Hcemonchus  (Strongylus) 
contortus,  is  another  important  intestinal  parasite  belonging 
to  the  group.  It  is  a  very  small  thread-like  species  occurring 
in  the  fourth  stomach  of  sheep,  cattle  and  goats.  The  larvae 
which  hatch  from  eggs  that  pass  out  with  the  feces  get  on  the 
grass  blades  and  so  into  the  stomach  of  new  hosts.  As  the 
infection  is  direct  the  disease  often  spreads  rapidly  and  does 
serious  damage,  particularly  to  lambs,  which  may  die  in  con- 
siderable numbers. 

Uncinariasis,  or  Hookworm  Disease. — Perhaps  no  other 
disease  has  attracted  so  much  attention  in  the  United  States 
during  the  past  few  years  as  the  hookworm  disease.  It 
is  caused  by  a  small  round-worm  from  one-half  to  four-fifths 
of  an  inch  in  length.  On  the  anterior  end,  which  is  bent 
back  giving  it  the  suggestive  hook  shape,  is  the  cup-like  mouth 
by  means  of  which  the  parasites  attach  themselves  to  the 
mucous  membrane  of  the  walls  of  the  intestine,  where,  in  ad- 
dition to  sucking  the  blood  of  the  victim  and  affecting  the 
mucous  membrane,  they  produce  a  poison  which  may  affect 
the  host  in  a  variety  of  ways.  The  most  pronounced  symp- 
toms are  anemia  and  aberrations  of  appetite.  The  skin  be- 
comes dry,  waxy  white,  or  dirty  yellow,  and  the  patient  may 
eat  too  little  or  too  much.  In  severe  cases  there  seems  to  be 
an  uncontrollable  desire  for  such  things  as  chalk,  rotten 

6 


82      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

wood,  sand,  gravel  and  all  kinds  of  dirt.  This  has  given  the 
popular  name  of  "dirt  eaters"  to  those  affected  with  this 
parasite. 

The  myriad  eggs  produced  by  the  adult  hookworms  pass 
out  of  the  body  of  the  host  with  the  feces,  and  if  these  fall  on 
the  ground  and  the  temperature  and  moisture  conditions  are 
suitable,  as  they  usually  are  in  the  tropical  and  semi-tropical 
regions  where  this  disease  is  worst,  the  young  larvae  soon  hatch 
and  grow  for  a  few  days  before  they  become  encysted.  In  this 
latter  condition  they  may  remain  for  some  time,  even  several 
months,  until  they  are  in  some  way  introduced  into  a  new 
host.  There  are  two  possible  ways  of  infection,  through  the 


FIG.  27. — Hookworm,  Necator  americanus.     a,  Male;  b,  female.     (Greatly 
enlarged;  after  Wilder.) 

mouth  or  through  the  skin  and  the  circulatory  system.  For  a 
long  while  it  was  thought  that  infection  was  wholly  through  the 
mouth,  but  it  is  now  known  that  this  is  not  even  the  usual 
mode  of  infection.  When  the  encysted  larvae  come  in  contact 
with  the  skin  of  some  person,  such  as  the  bare  foot  of  a  child, 
they  break  from  their  covering  and  burrow  their  way  into  the 
skin  through  some  of  the  pores  or  hair  follicles.  They  soon 
find  their  way  into  the  circulation  and  later  into  the  lungs  or 
larynx  and  finally  are  swallowed  and  attach  themselves  to  the 
walls  of  the  alimentary  canal. 

In  passing  through  the  skin  they  produce  certain  symptoms 
commonly  known  as  ground  itch  which  often  causes  much 
suffering.  It  will  be  seen  that  children  are,  under  ordinary 


TRICHINA,  HOOKWORMS,  FILARIA,  ETC.       83 

circumstances,  more  subject  to  attack  than  adults  because 
they  go  barefoot  more,  but  adults  are  in  no  wise  immune,  and 
in  mining  regions  men  may  furnish  the  highest  percentage  of 
infection  because  conditions  in  the  mines  are  favorable  for  the 
development  of  the  parasite. 

Epsom  salts  followed  by  thymol  and  then  by  epsom  salts 
again  will  remove  the  worms  from  the  body  of  the  host,  but 
reinfection  may  again  take  place  unless  sanitary  measures  are 
adopted  to  control  the  spread  of  the  pest.  Where  the  modern 
sewage  facilities  are  found  no  hookworms  occur,  and  the  great 
fight  that  is  being  made  against  this,  the  worst  curse  of  the 
poorer  classes  of  the  south,  is  made  against  the  unsanitary 


FIG.  28. — Section  through  the  skin  of  a  dog  two  hours  after  it  has 
been  infected  with  the  Old  World  hookworm.  (Greatly  enlarged;  after 
Wilder.) 


conditions  that  exist  in  many  regions.  If  the  soil  is  not 
polluted  with  the  feces  that  contain  the  eggs  of  the  parasite 
the  disease  will  not  spread. 

Not  only  do.  the  hookworms  directly  cause  many  deaths 
each  year,  but  they  lower  the  vitality  of  the  victims  so  that 
they  become  an  easy  prey  to  other  diseases.  In  addition 
they  retard  their  physical  and  intellectual  development,  seri- 
ously affect  the  working  capacity  and  in  many  other  ways 


84      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

exert  a  baneful  influence  on  the  general  health  and  longevity 
and  on  the  material  welfare  of  the  people. 

Porto  Rico  has  suffered  severely  from  this  disease,  as  indeed 
have  nearly  all  tropical  and  sub-tropical  countries.  In  the 
old  world  the  most  common  species  of  hookworm  is 
Uncinaria  duodenalis.  In  the  United  States  Necator 
(Uncinaria)  americanus  is  the  most  abundant.  Both  of  these 
species  were  formerly  included  in  the  genus  Ankylostomum 
and  so  the  disease  that  they  cause  is  frequently  called 
ankylostomiasis. 

Several  of  our  domestic  animals  are  infected  with  other 
species  of  hookworms.  Uncinariasis,  or  "salt  sick,"  or  hook- 
worm disease  of  cattle,  is  a  very  serious  disease  in  some  of  the 
southern  states.  This  disease  can  be  partially  controlled  by 
intelligent  methods  of  handling  the  stock.  As  it  occurs  chiefly 
on  low  wet  lands  the  selection  of  pasture  lands  is  of  first 
importance,  or  rather  it  is  of  second  importance,  for  the  most 
important  thing  of  all  is  to  keep  the  disease  out  altogether  by 
not  allowing  infected  cattle  to  come  on  the  farms  or  into  the 
locality. 

A  species  of  hookworm  occurring  in  fur  seals  often  causes  a 
loss  of  thousands  of  the  young  or  pup  seals  each  year  on  the 
breeding  grounds. 

Filaria  and  Elephantiasis. — Another  genus  of  very  serious 
Nematode  parasites  is  known  as  Filaria.  The  filariae  cause  the 
various  forms  of  disease  known  as  filariasis.  Filaria  bancrofti 
is  the  name  of  a  minute,  transparent,  little  worm  that  occurs  in 
human  blood  and  lymph  in  many  tropical  and  sub-tropical 
regions,  extending  often  into  temperate  climates.  The  larval 
forms,  that  occur  in  the  blood,  are  but  a  little  more  than 
one  one-hundredth  of  an  inch  long  and  about  as  big  around 
as  a  blood  corpuscle.  During  the  day  time  but  few  of  these 
are  to  be  found  in  the  blood  near  the  surface  of  the  body, 
but  as  evening  comes  on  they  may  be  found  there  in  in- 
creasing numbers. 

This  night-swarming  to  the  peripheral  circulation  has  been 
found  to  be  a  remarkable  adaptation  in  the  life  history  of  the 
parasite  to  the  presence  of  night-flying  mosquitos,  for  it  has 
been  demonstrated  that  in  order  to  go  on  with  their  develop- 


TRICHINA,  HOOKWORMS,  FILARIA,  ETC.       85 

ment  these  larval  forms  must  be  taken  into  the  alimentary 
canal  of  a  mosquito.  There  they  undergo  certain  changes, 
and  then  make  their  way  through  the  walls  of  the  stomach 
into  the  muscles,  where  they  increase  in  size  until  they  are 
about  one-sixteenth  of  an  inch  in  length.  Later  they  migrate 
to  other  parts  of  the  body,  some  of  them  to  the  proboscis  of 
the  mosquito  from  which  they  issue  when  the  mosquito  is 
feeding  and  thus  gain  entrance  into  another  host.  It  is  not 
known  that  these  parasites  can  gain  an  entrance  into  the 
circulatory  system  in  any  other  way, 
but  it  has  been  suggested  that  mosqui- 
tos  dying  in  the  water  may  liberate 
some  of  the  filariae  which  may  later 
find  their  way  into  the  vertebrate  host 
when  the  water  is  used  for  drinking. 

Soon  after  entering  the  circulatory 
system  of  the  human  host  the  parasites 
make  their  way  into  the  lymphatics 
where  they  attain  sexual  maturity, 

and  in  due  time   new  generations  of      FlG-      29.— Microfilaria 
,11          i    r-i  j~i  of    the    blood:     immature 

the  larval  filariae,  or  microfilariae,  are  stage  of  Fila'ria  bancroftL 

poured   into   the   lymph,    and    finally   (Greatly     enlarged;  after 

into  the  definite  blood-vessels,  ready  Terzi-) 

to  be   sucked   up   by  the  next  mosquito  that  feeds  on  the 

patient. 

In  most  cases  of  infection  the  presence  of  these  filariae  in  the 
blood  seems  to  cause  no  inconvenience  to  the  host.  They 
are  probably  never  injurious  in  the  larval  stage,  that  is,  in  the 
stage  in  which  they  are  found  in  the  peripheral  circulation. 

In  many  cases,  however,  the  presence  of  the  sexual  forms  in 
the  lymphatics  may  cause  serious  complications.  The  most 
common  of  these  is  that  hideous  and  loathsome  disease  known 
as  elephantiasis,  in  which  certain  parts  of  the  patient  become 
greatly  swollen  and  distorted.  An  arm  or  a  leg  may  become 
swollen  to  several  times  its  natural  size,  or  other  parts  of  the 
body  may  be  seriously  affected.  This  disease  occurs  most 
commonly  in  tropic  and  sub-tropic  regions.  Nearly  one-third 
of  the  natives  of  the  Samoan  Islands  suffer  from  elephantiasis. 


86      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  guinea-worm,  Filaria  medinensis,  referred  to  on  an 
earlier  page,  is  a  member  of  this  group.  It  has  been  known  for 
many  ages,  and  is  thought  to  be  the  "  fiery  serpent"  mentioned 
by  Moses.  It  lives  in  the  connective  tissues,  where  it  attains 
a  length  of  two  or  three  feet.  Its  diameter  is  about  one  and 
one-half  millimeters.  When  it  is  ready  to  produce  young  it 
usually  descends  to  the  feet  or  the  lower  part  of  the  legs  of  the 
host  or  the  part  most  likely  to  come  in  contact  with  the  water. 
Here  it  burrows  out  to  the  surface,  often  producing  serious 
sores.  The  intermediate  stage  is  passed  in  the  body  of 
Cyclops,  a  small  fresh- water  crustacean. 

There  are  several  other  species  of  Filaria  that  are  parasitic 
in  man  but  they  are  of  less  importance.  Filaria  loa  is  an  inter- 
esting species  that  lives  in  the  connective  tissue  just  under 
the  skin  and  travels  about  from  one  part  of  the  body  to 
another,  occurring  most  commonly  about  the  eyes,  where 
their  presence  may  cause  irritation  and  congestion. 

Classification  of  Nemathelminthes. — This  branch  may  be 
divided  into  three  classes,  the  Nematoda,  Nematomorpha  and 
Acanthocephala.  The  class  Ch&tognatha  (Gr.  chaite,  hair; 
gnathos,  cheek)  or  arrow-worms,  is  usually  included  in  this 
branch  but  the  relationship  of  the  group  is  very  uncertain. 

The  Nematoda  (Gr.  nema,  thread;  eidos,  likeness)  are  by 
far  the  most  important  and  include  all  of  the  forms  that  have 
just  been  described,  with  the  exception  of  the  hair-snakes  which 
belong  to  the  second  class. 

The  Nematomorpha  (Gr.  nema,  a  thread;  morphe,  form) 
include  the  hair-snakes,  the  larvae  of  which,  as  we  have  already 
noted,  are  parasitic  in  insects.  One  common  species,  Mermis 
albicans,  frequently  occurs  abundantly  enough  in  grass- 
hoppers to  be  of  some  importance  in  their  control.  It  is 
probably  this  species,  too,  that  at  times  causes  so  much  alarm 
in  some  regions  when  the  "cabbage  snakes"  appear  in  great 
numbers.  When  these  round-worms  occur  on  cabbages  or 
other  vegetables  it  means  that  the  insect  that  acted  as  their 
host  was  probably  resting  or  feeding  on  the  plant  when  the 
parasite  left  it.  As  soon  as  they  can  they  pass  into  the  ground 


TRICHINA,  HOOKWORMS,  FILARIA,  ETC.       87 


and  do  not  injure  the  vegetables.     No  harm  will  come  from 
eating  vegetables  that  have  been  visited  by  these  parasites. 

The  Acanthocephala  (Gr.  akantha,  thorn;  kephale,  head),  or 
thorn-headed  worms,  include  a  number  of  parasitic  forms 
which  show  extreme  specialization  in  their  mode  of  life.  The 
anterior  end  is  developed  into  a  conspicuous  spiny  organ  for 
holding  on  to  the  walls  of  the  alimentary  canal  of  the  hosts  in 
which  they  live.  There  is  no  mouth  or  digestive  organs  but 
the  parasite  takes  its  nourishment  through 
the  body-wall  from  the  food  surrounding  it. 

Echinorhynchus  gigas,  infesting  hogs,  is 
the  best  known  species  of  this  class.  In 
America  the  larvae  of  the  June  beetle,  Lack- 
nosterna,  which  is  the  common  white  grub 
found  in  the  sod  in  pasture  lands  and  else- 
where, serves  as  the  intermediate  host  for 
the  parasite.  Hogs  should  not  be  allowed 
to  pasture  on  lands  where  the  grubs  have  be- 
come infected  from  previously  infested  hogs. 
Once  pasture  land  has  become  infected  it 
should  be  left  for  three  years  to  insure  the 
maturing  of  all  the  grubs  that  are  infected. 

Several  other  species  belonging  to  this 
class  are  parasites  of  fishes.  living  specimen.) 

ANIMALS  OF  UNCERTAIN  RELATIONSHIP 

There  are  two  groups  of  aquatic  animals  the  exact  relation- 
ships of  which  are  by  no  means  agreed  upon  by  systematic 
zoologists.  They  are  usually  supposed  to  be  more  nearly 
related  to  the  worms  than  to  any  other  group,  and  as  they  are 
not  of  enough  economic  importance  to  be  given  a  separate 
chapter  they  may  be  mentioned  here. 

The  Wheel  Animalcules,  or  Rotifers,  branch  Trochel- 
minthes  (Gr.  trochos,  wheel;  helmins,  worm).  These  are 
minute  aquatic  animals  which  on  account  of  their  size  were  for 
a  long  time  classed  with  the  Protozoa.  But  they  are  really 
very  complex  in  structure.  The  anterior  end  is  provided  with 


FIG.   30.  —  A 
wheel  animalcule, 


88      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

a  circlet  of  vibrating  cilia,  which  has  suggested  the  common 
name.  These  little  animals  are  interesting  on  account  of  their 
remarkable  power  to  withstand  drying.  When  the  water  in 
which  they  are  found  evaporates,  some  of  them  do  not  die  but, 
as  minute  shrivelled  dust-like  particles,  may  lie  for  months 
or  even  years  and  be  revived  again  when  water  reaches  them. 
The  Sea-mats  and  the  Lamp -shells,  Branch  Molluscoida 
(Mollusca,  mollusc;  Gr.  eidos,  likeness). — The  sea-mats,  or 
Polyzoa,  are  common  on  rocks  along  the  seashore  and  sometimes 
in  fresh  water  also.  Most  of  them  either  spread  mat-like 
over  the  surface  of  the  objects  on  which  they  are  growing,  or 
form  branched  tree-like  or  moss-like  colonies  and  look  much 
more  like  plants  than  animals.  Only  their  development 
suggests  any  relation  to  the  worms.  The  lamp-shells,  or 
Brachiopoda,  are  all  marine.  They  look  so  much  like  little 
clams  that  for  a  long  time  they  were  classed  with  the  molluscs. 
Their  chief  interest  lies  in  the  fact  that  they  represent  a  group 
of  animals  that  were  once  very  numerous  but  which  have  not 
been  able  to  adapt  themselves  to  the  changed  conditions  that 
are  found  on  the  earth  to-day.  In  ages  past  they  seem  to  have 
occurred  in  great  numbers,  as  more  than  a  thousand  species 
have  been  preserved  as  fossils  in  the  rocks.  To-day  only 
about  one  hundred  species  are  known,  and  some  of  these  are 
very  rare. 


CHAPTER  XIII 
STARFISHES,  SEA-URCHINS  AND  SEA-CUCUMBERS 

The  starfishes,  sea-urchins,  sand-dollars  and  sea-cucumbers, 
branch  Echinodermata  (Gr.  echmos,  hedgehog;  derma,  skin), 
compose  the  only  branch  of  animals  all  of  whose  members 
are  exclusively  marine.  Although  they  are  among  the  most 
common  inhabitants  of  all  sea  beaches  no  species  has  adapted 
itself  to  life  in  fresh  water.  Why  this  is  so  no  one  is  yet  able 
to  explain.  Most  of  them  can  move  about  freely  but  some  of 
the  feather  stars  are  attached  to  rocks  or  other  objects  as  the 
polyps  are. 

The  Starfish. — The  common  five-rayed  starfish  well  illus- 
trates the  general  plan  of  structure  of  members  of  this  group. 
The  five  rays  arranged  around  the  central  disk  illustrate  the 
radial  symmetry  which  is  characteristic  of  the  branch.  The 
entire  aboral  or  upper  surface,  as  well  as  a  greater  part  of 
the  oral  or  lower  side,  is  thickly  studded  with  the  calcareous 
plates,  or  ossicles,  of  the  body-wall.  These  ossicles  support 
many  short,  stout  spines  arranged  in  irregular  rows,  and 
numerous  pincer-like  processes,  the  pedicellaria.  In  the  inter- 
spaces between  the  calcareous  plates  are  soft  fringe-like  pro- 
jections of  the  inner  body-lining,  the  respiratory  caeca.  A  little 
to  one  side  of  the  center  of  the  disk  is  the  small  striated  cal- 
careous madreporic  plate,  and  a  little  nearer  the  center  is  the 
anal  opening.  At  the  tip  of  each  arm  or  ray  is  a  cluster  of 
small  calcareous  ossicles  and  within  each  cluster  a  small  speck 
of  red  pigment,  the  eye-spot  or  ocellus. 

On  the  oral  (under)  surface  are  the  centrally-located  mouth, 
and  the  ambulacral  grooves  running  longitudinally  along  each 
ray.  In  each  groove  are  two  double  rows  of  soft  tubular 
bodies  with  sucker-like  tips.  These  are  called  the  tube-feet, 
and  are  organs  of  locomotion. 


90      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

By  removing  all  of  the  dorsal  body-wall  except  the  part 
surrounding  the  madreporic  plate  and  the  anus,  the  internal 


— -eye  spot 


nuscles  of  the  fylorif  caeca, 


musclei  of  the  pyloric  caeca 


eye  spot  --J 


FIG.  31. — Dissection  of  a  starfish,  Asterias  sp.  male. 

organs  are  exposed.     The  large  alimentary  canal  is  divided 
into  several  regions.      The  short  esophagus  leads  from  the 


STARFISHES,  SEA-URCHINS,  ETC.  91 

mouth  directly  into  a  large  membranous  pouch,  the  cardiac 
portion  of  the  stomach.  By  a  short  constriction  the  cardiac 
portion  is  separated  from  the  part  which  lies  just  above,  i,  e., 
the  pyloric  portion  of  the  stomach.  From  the  pyloric  portion 
large,  pointed,  paired  glandular  appendages,  the  pyloric  caca, 
extend  into  each  ray.  Their  function  is  digestive,  and  some- 
times they  are  spoken  of  as  the  digestive  glands  or  "livers." 
The  pyloric  cceca,  as  well  as  the  cardiac  portion  of  the  stomach, 
are  held  in  place  by  paired  muscles  which  extend  into  each 
arm.  The  pyloric  portion  of  the  stomach  opens  above  into 
a  short  intestine  which  terminates  in  the  anus.  Attached 
to  the  intestine  is  a  convoluted  many-branched  tube,  the 
intestinal  c&cum. 

In  the  angle  of  each  two  adjoining  rays  are  paired  glandular 
reproductive  organs,  which  empty  by  a  common  duct  on  the 
aboral  surface.  The  small  bulb-like  bladders  extending  in  two 
double  rows  on  the  floor  of  each  ray  are  the  water-sacs,  or  am- 
pulla, and  each  one  is  connected  directly  with  one  of  the  tube- 
feet. 

Passing  around  the  alimentary  canal  near  the  mouth  is  a 
ring-shaped  canal  from  which  the  radial  vessels  run  out  be- 
neath the  floor  of  each  ray  and  from  which  a  hard  tube  extends 
to  the  madreporic  plate.  This  hard  tube  is  the  stone  canal,  so 
called  because  its  walls  contain  a  series  of  calcareous  rings, 
while  the  circular  tube  is  the  ring  canal  or  circum-oral  water- 
ring,  from  which  radiate  the  radial  canals.  In  some  species  of 
starfish  there  are  bladder-like  reservoirs,  Polian  vesicles,  which 
extend  interradially  from  the  ring  canal. 

The  ampullae  and  tube-feet  are  all  connected  with  the  radial 
canals.  By  the  contraction  of  the  delicate  muscles  in  the 
walls  of  the  ampullae  the  fluid  in  the  cavity  is  compressed, 
thereby  forcing  the  tube-feet  out.  By  the  contraction  of 
muscles  in  the  tube-feet  they  are  again  shortened,  while  the 
small  disk-like  terminal  sucker  clings  to  some  firm  object. 
In  this  way  the  animal  pulls  itself  along  by  successive  " steps." 
This  entire  system,  called  the  water-vascular  system,  is  char- 
acteristic of  the  branch  Echinodermata.  In  addition  to  the 
fluid  in  the  water-vascular  system  there  is  yet  another  body- 


92      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


fluid,  the  peri-visceral  fluid,  which  bathes  all  of  the  tissues  and 
fills  the  body-cavity. 

The  perivisceral  fluid  is  aerated  through  the  respiratory  caeca 
which,  as  we  have  seen,  are  outpocketings  of  the  thin  body- 
wall  which  extend  outward  between  the  calcareous  plates  of 
the  body.  Surrounding  the  stone  canal  is  a  thin  membranous 
tube,  and  within  and  by  the  side  of  the  stone  canal  is  a  soft 
tubular  sac.  The  functions  of  these  organs  are  not  certainly 
known. 

calcareous  spine  respiratory  caeca 

epithelium  of  the  body     '  **  """"  " 

cavity 


mesentery- 
pyloric  caecumr 


—ossicles 


— ampulla 


tube  fool 


ambulacral  ossicle 

ectodermal  covering — 

\M 

/         I 
Hb         x 

pedicellaria — • 

.  radial  'canal     / 
radial  blood-vessel 

FIG.  32. — Semi-diagrammatic   figure   of   cross-section   of   the   ray   of  a 

starfish,  Asterias  sp. 

The  nervous  system  consists  of  a  nerve-ring  about  the  mouth, 
and  nerves  running  from  this  ring  beneath  the  radial  canals 
along  each  arm. 

The  starfish  feed  upon  other  marine  animals,  especially  on 
molluscs.  They  are  often  very  destructive  on  oyster  beds, 
where  they  may  occur  in  such  numbers  as  wholly  to  deplete 
the  beds  unless  they  are  removed  by  means  of  rakes  or  tangles 
of  ropes  that  are  dragged  over  the  beds  for  this  purpose. 

When  the  starfish  wishes  to  feed  on  a  mollusc  that  is  too 


STARFISHES,  SEA-URCHINS,  ETC.  93 

large  to  be  taken  into  its  mouth  the  stomach  is  extended 
through  the  mouth  and  the  living  prey  is  covered  over  by  it. 
As  soon  as  the  shell  is  opened  ever  so  little  the  soft  parts  of 
the  victim  are  sucked  up  and  digested  by  the  starfish.  Having 
finished  its  meal  the  starfish  draws  its  stomach  in  and  seeks 
another  oyster  or  clam. 


FIG.  33. — Regeneration  of  starfishes,  Linckia  sp.  Upper  figure  shows 
a  starfish  regenerating  arms  that  have  been  lost;  the  lower  figure  shows  a 
portion  of  an  arm  regenerating  the  disk  and  other  arms.  (About  natural 
size.) 

Starfish,  and  in  fact  most  of  the  Echinoderms,  have  the 
power  of  regenerating  lost  parts.  If,  through  accident,  a 
starfish  loses  one  or  more  of  its  rays  new  ones  will  grow  out 
to  replace  the  old  ones,  or,  in  some  cases,  the  arm  may  prac- 


94      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

tically  regenerate  all  the  rest  of  the  body.  Specimens  showing 
this  process  are  sometimes  found  on  the  beaches.  Fig. 
33  shows  such  specimens  found  on  the  reefs  in  Samoa. 

During  its  development  from  the  egg  to  the  adult  the 
starfish  passes  through  a  remarkable  metamorphosis.  The 
young  when  it  issues  from  the  egg  is  more  or  less  ellipsoidal,  and 
is  active  and  free-swimming,  being  provided  with  numerous 
cilia.  This  larva  soon  changes  to  another  curious  form  with 


FIG.  34. — A  sea-urchin,  Strongylocentrotus  franciscanns,  showing  movable 
spines.     (Reduced.) 

many  prominent  projections.  This  is  so  unlike  a  starfish 
that  the  earlier  naturalists  did  not  realize  that  the  larvae  were 
in  any  way  related  to  the  starfish  and  gave  them  the  name 
Bipinnaria,  thinking  they  were  fully  developed  adult  animals. 
The  name  is  still  used  in  referring  to  starfish  larvae,  but  we  now 
know  that  the  bipinnaria  become,  by  later  development, 
adult  starfish. 

Other  Echinoderms. — All  the  various  starfish  belong  to  the 
class  Aster oidea  (Gr.  aster,  star;  eidos,  likeness)  and  although 
they  may  differ  much  in  general  appearance  they  are  all  readily 


STARFISHES,  SEA-URCHINS,  ETC.  95 

recognized.  Some  starfish  may  have  thirty  or  more  rays 
instead  of  five  as  in  the  typical  forms.  Others  may  have  the 
interradial  spaces  filled  out  nearly  or  quite  to  the  tips  of  the 
rays,  making  the  animal  simply  a  pentagonal  disk.  Some 
are  very  small,  less  than  an  inch  in  diameter,  while  others 
attain  an  extent  of  three  feet  or  more. 

The  brittle-stars  belong  to  the  class  Ophiuroidea  (Gr.  ophis, 
snake;    our  a,    tail;    eidos,    likeness).     They    differ   from    the 


FIG.  35. — A  holothurian  or  sea-cucumber,  Cucumaria  frondosa.     (About 
j  natural  size.) 

Aster oidea  in  that  the  body-cavity  does  not  extend  out  into 
the  arms  as  it  does  in  the  starfish,  or  extends  at  most  only  into 
the  bases  of  the  arms.  The  five  radiating  rays  are  usually 
slender,  more  or  less  cylindrical,  and  sometimes  branched. 

The  sea-urchins,  class  Echinoidea  (Gr.  echlnos,  hedgehog; 
eidos,  likeness),  look  quite  unlike  the  starfish.     The  body  is 


96      ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

globular,  usually  more  or  less  flattened  at  the  poles.  It 
is  covered  with  many  movable  spines  which  may  be  small 
and  light  or  long  and  heavy.  When  the  spines  are  removed 
the  calcareous  plates  that  constitute  the  firm  part  of  the  body- 
wall  are  plainly  distinguished.  Sea-urchins  are  found  mostly 
in  tide  pools  near  the  shore,  but  some  occur  at  great  depths. 


FIG.  36. — A  sea-lily,  Pcntacrinus  sp.     (About  i  natural  size.) 

The  sand-dollars  or  cake-urchins  belong  to  the  same  class. 
Their  bodies  are  very  much  flattened  and  often  brightly 
colored.  They  are  common  in  the  sand  on  both  the  Atlantic 
and  Pacific  coasts. 

The  sea-cucumbers,  class  Holothuroidea  (Gr.  holos,  whole; 
thouros,  rushing;  eidos,  likeness), look  even  less  like  starfish. 


STARFISHES,  SEA-URCHINS,  ETC.  97 

The  body  is  more  or  less  cylindrical  and  looks  not  unlike  a 
cucumber,  perhaps  still  more  like  a  sausage.  The  body-wall 
is  tough  arid  leathery  and  the  five  rows  of  tubular  feet  are 
usually,  but  not  always,  present.  At  one  end  is  a  ring  of 
branched  tentacles  surrounding  the  mouth.  These  are  often 
flower-like  or  leaf-like  and  brightly  colored.  In  the  Orient 
sea-cucumbers  are  largely  used  as  food,  the  gathering  and 
preparing  of  this  trepang,  as  it  is  called,  forming  a  very  con- 
siderable industry. 

Many  of  the  feather-stars  or  sea-lilies,  class  Crinoidea  (Gr. 
krinon,  lily;  eidos,  likeness),  are  fixed  to  rocks  or  the  sea  bottom 
by  a  longer  or  shorter  stalk  which  is  composed  of  a  number  of 
segments.  Others  are  attached  by  a  stalk  during  their  larval 
stage,  but  after  a  time  the  stalk  is  absorbed  and  the  feather  star 
becomes  free.  The  central  disk  is  provided  with  a  number  of 
radiating  arms  which  are  long  and  slender,  sometimes  re- 
peatedly branched.  The  fine  lateral  pinnules  on  these  arms 
give  them  a  feather-like  appearance.  They  occur  mostly 
in  deep  water.  There  are  comparatively  few  species  of  crinoids 
that  still  exist,  but  in  former  geologic  times  thousands  of 
species  flourished.  The  fossilized  parts  of  their  bodies, 
especially  the  little  disk-like  segments  of  the  stem,  are  very 
common  in  Paleozoic  rocks. 


CHAPTER  XIV 

EARTHWORMS,  LEECHES  AND  OTHER  SEGMENTED 

WORMS 

The  segmented  worms  (branch  Annelida,  annellus,  little 
ring),  of  which  the  earthworm  is  the  most  common  example, 
show  a  decided  advance  in  structure  over  the  flat-worms  and 
round-worms.  Their  bodies  are  divided  into  a  series  of  seg- 
ments, and  most  of  them  have  well  developed  nervous  and 
circulatory  systems.  There  is  a  definite  body-cavity,  and 
paired  organs  of  excretion  called  nephridia. 

The  segmented  worms  are  grouped  in  four  classes,  the 
Chatopoda  (Gr.  chaite,  hair;  fious,  foot)  including  the  earth- 
worms and  many  marine  worms;  the  Hirudinea  (L.  hirudo, 
leech)  or  leeches;  and  the  marine  Archiannelida  (Gr.  archi-, 
primitive;  annellus,  little  ring)  and  Gephyrea  (Gr. '  gephyrd, 
bridge). 

The  Earthworm. — In  the  Chcetopoda  the  sides  of  the  body 
are  furnished  with  minute  setae,  or  with  special  locomotor 
protrusions  known  as  parapodia.  The  familiar  earth-worm,  or 
angle-worm,  or  fish-worm,  as  it  is  often  called,  will  serve  as  an 
example  of  the  group.  Earth-worms  eat  their  way  through  the 
ground  forming  definite  burrows  and  bringing  to  the  surface 
soil  from  considerable  depths.  The  earth  that  is  swallowed  as 
they  are  digging  contains  more  or  less  decaying  vegetable  matter 
which  is  used  as  food.  Darwin  was  the  first  to  call  attention  to 
the  great  good  that  the  earthworms  do  by  opening  up  the 
soil  so  water  can  enter,  enabling  plant  roots  to  penetrate 
deeper,  and  by  bringing  to  the  surface  soil  from  which  the 
various  plant  foods  have  not  yet  been  taken  by  the  plants. 
He  estimated  that  in  England — and  conditions  are  prac- 
tically the  same  in  America — about  ten  tons  of  soil  per 
acre  pass  annually  through  the  bodies  of  these  worms,  and 

98 


EARTHWORMS,  LEECHES,  ETC.  99 

that  they  cover  the  surface  with  earth  at  the  rate  of  about  an 
inch  in  five  or  six  years.  Besides  being  an  important  factor  in 
increasing  the  fertility  of  the  soil  the  earthworms  furnish  a 
considerable  part  of  the  food  supply  of  many  birds.  Nor 
should  we  fail  to  mention  the  important  part  that  they  play 
in  the  welfare  of  mankind,  or  rather  "boykind,"  when,  dan- 
gling from  a  hook,  they  tempt  the  hungry  fish  from  its  haunts 
in  the  shade  of  the  rocks  or  among  the  gnarled  roots  of  the  old 
tree.  Usually  they  remain  in  the  ground  during  the  day, 
wandering  about  only  at  night,  but  sometimes,  particularly 
after  heavy  rains,  they  may  be  found  in  considerable  numbers 
crawling  over  the  ground  in  the  early  morning.  As  they  are 
often  found  on  hard  pavements  where  they  have  crawled  or 
been  washed  by  the  water  many  persons  think  that  they  have 
"rained  down." 

External  Structure. — The  body  of  the  earthworm  is  long, 
cylindrical,  bluntly  pointed  at  the  anterior  end  and  rounded 
and  flattened  at  the  posterior  end.  The  four  double  rows  of 
stiff  bristles  or  setae  are  hardly  visible  to  the  naked  eye  but 
they  may  be  detected  by  drawing  the  worm  backward  across 
the  hand.  Over  the  mouth  is  a  small  lobe  called  the  prosto- 
mium,  and  a  short  distance  behind  it  is  a  broad  thickened  ring 
or  girdle,  the  clitellum.  This  is  a  glandular  structure  which 
secretes  the  cases  in  which  the  eggs  are  laid. 

Internal  Structure. — If  a  careful  incision  is  made  along  the 
dorsal  line  extending  from  behind  the  clitelleum  to  the  anterior 
end  of  the  body  the  sides  of  the  body-wall  may  be  fastened 
aside  so  as  to  expose  the  internal  organs.  The  body-wall  is 
made  up  of  a  thin  transparent  covering,  the  cuticle,  just  be- 
neath which  is  a  less  transparent  layer,  the  epidermis,  and  two 
layers  of  muscles,  an  outer  circular  layer  and  an  inner  longi- 
tudinal layer.  The  space  between  the  body-wall  and  the 
alimentary  canal  is  the  body-cavity,  or  ccdom.  It  is  divided 
into  sections  or  segments  by  thin  membranes,  the  septa.  The 
body  of  the  earthworm  may  be  compared  to  two  tubes,  a 
larger  outer  one  represented  by  the  body-wall  and  a  smaller 
inner  one,  the  alimentary  canal,  extending  from  one  end 
to  the  other.  The  space  between  these  is  the  body-cavity. 


ioo    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

cerebral  ganglion 


retractor  and  protractor 
muscles  of  the  pharynx 

cesophageal  pouches— « 
seminal  receptacle 
seminal 


aniis \ 


pharynx 
psophagua 


FIG.  37. — Dissection  of  the  earthworm,  Lumbricus  sp. 


EARTHWORMS,  LEECHES,  ETC.  101 

This  is  an  arrangement  that  we  find  common  in  all  the  higher 
animals. 

In  the  alimentary  canal  a  number  of  distinct  parts  may  be 
recognized.  Anteriorly  is  the  muscular  pharynx,  which  is 
followed  by  a  narrow  esophagus  leading  directly  into  the 
thin-walled  crop;  next  comes  the  muscular  gizzard,  and  next 
the  intestine,  which  opens  externally  in  the  terminal  segment 
through  the  anus.  The  anterior  end  of  the  alimentary  canal 
is  more  or  less  protrusible,  while  the  posterior  portion  is  held 
more  firmly  in  place  by  the  septa,  which  act  as  mesenteries. 
Surrounding  the  narrow  esophagus  are  the  reproductive  organs, 
three  pairs  of  large  white  bodies  and  two  pairs  of  smaller  sacs. 
Under  the  reproductive  organs  are  three  pairs  of  bag-like 
structures  projecting  from  the  esophagus.  The  front  pair 
are  the  esophageal  pouches;  the  next  two  pairs  are  the  esopha- 
geal,  or  calcijerous,  glands.  They  communicate  with  the 
alimentary  canal,  and  secrete  a  milky  calcareous  fluid. 

By  cutting  transversely  through  the  alimentary  canal  in  the 
region  of  the  clitellum,  a  dorsal  fold  of  the  intestine,  the 
typhlosole,  may  be  seen  extending  into  the  lumen.  This  fold 
gives  a  greater  surface  for  digestion,  and  in  it  are  a  great 
many  hepatic  or  special  digestive  cells.  The  entire  alimentary 
canal  is  lined  internally  with  epithelium. 

The  dorsal  blood-vessel  lies  along  the  dorsal  surface  of  the 
alimentary  canal.  From  the  anterior  portion  there  arise 
several  circumesophageal  rings,  or  "  hearts."  These  hearts 
are  contractile,  and  serve  to  keep  the  blood  in  motion  through 
the  blood-vessels.  Just  beneath  the  alimentary  canal  is  the 
ventral  blood-vessel,  and  still  beneath  this  the  ventral  nerve-cord. 
The  slight  swellings  on  the  nerve-cord  in  each  segment  of  the 
body  are  the  ganglia.  The  brain,  or  cerebral  ganglion,  lies  in 
the  first  segment  of  the  body  above  the  esophagus,  and  is  con- 
nected with  the  ventral  nerve  chain  by  the  circumesophageal 
collar. 

The  excretory  system  is  peculiar,  consisting  of  a  series  of  small 
convoluted  tubes,  the  inner  ends  of  which  are  furnished  with 
small  ciliated  funnels  which  gather  and  carry  off  the  waste 
matter  from  the  fluid  that  fills  the  body-cavity.  There  are 


102    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

no  special  organs  of  respiration,  but  the  thin  walls  of  the  skin 
are  traversed  by  a  network  of  minute  blood-vessels  which 
are  separated  from  the  air  by  only  a  very  thin  membrane 
through  which  the  oxygen  passes  readily  and  the  carbon 
dioxide  is  given  off. 


nephridium  f^rsal  ttotd  vessel 

\     hepatic  cells   / 

\         \  i  longitudinal  muscle 

'.  \  /       firmlnr  miiscle   fit 


I/ 

ft    jcircular  muscle  fibres 
epidermis 
.cuticle 


typhlosole 


nephridipore  !  nephrostome     \ 

•  ventral  vessel 

body  cavity 

FIG.  38. — Cross-section  of  earthworm. 


The  earthworm  is  hermaphroditic,  that  is,  both  spermatozoa 
and  ova  are  produced  in  the  same  individual.  The  testes  are 
two  pairs  of  flattened  glands  lying  in  the  region  of  the  tenth  and 
eleventh  segments.  These  are  connected  with  the  seminal 
vesicles  and  communicate  with  the  exterior  through  the  long 
vasa  deferentia  which  open  in  the  fifteenth  segment.  The  ovaries 
are  attached  to  the  septa  separating  the  twelfth  and  thirteenth 
segments.  The  ova  reach  the  exterior  through  a  pair  of  funnel- 
shaped  oviducts,  the  mouths  of  which  are  near  the  ovaries. 


EARTHWORMS,  LEECHES,  ETC  103 

They  pass  through  the  septum  between  the  thirteenth  and 
fourteenth  segments  and  open  through  the  ventral  wall  of  the 
fourteenth  segment.  The  sperm  cells  do  not  fertilize  the  ova 
from  the  same  individual.  When  the  reproductive  elements 
are  ripe,  two  worms  mate  and  there  is  a  transference  of 
spermatozoa  from  each  individual  to  the  other.  The  clitellum 
then  becomes  very  much  swollen,  and  finally  forms  a  collar- 
like  structure  about  the  body  of  the  worm.  As  this  slips 
forward  the  ova  are  discharged  into  it,  and  a  little  further 
forward  the  sperm  cells  that  have  been  received  during 
copulation  are  also  emptied  into  it.  As  it  passes  on  over  the 


FIG.  39. — A  group  of  marine  worms.  At  the  left  a  gephyrean,  Dendro- 
stomum  cronjhelmi,  the  upper  right-hand  one  a  nereid,  Nereis  sp.,  the  lower 
right-hand  one,  Polynce  brevisetosa.  (From  living  specimens  in  a  tide- 
pool  in  the  Bay  of  Monterey,  California.) 


head  both  ends  of  the  collar  become  sealed  and  thus  a  capsule 
containing  the  ova  and  spermatozoa  is  formed.  This  capsule 
lies  in  the  ground  until  the  young  are  hatched.  Only  a  part 
of  the  eggs  in  each  capsule  develop,  the  rest  being  used  for  food 
by  the  growing  young. 

The  Marine  Worms. — To  the  genus  Nereis  belong  many  of 
the  large  marine  worms  that  are  found  on  almost  all  sea 
beaches.  The  head  is  provided  with  two  pairs  of  eyes  and 
with  several  tentacles  which  act  as  feelers.  The  sides  of  the 


io4    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


body  are  provided  with  lateral  plates,  a  pair  to  each  segment. 
These  plates  are  divided  into  lobes,  and  aid  the  animal  in 
crawling  or  swimming,  and  as  some  of  them  are  well  pro- 
vided with  blood-vessels  they  also  serve  as  respiratory  organs. 
Many  of  the  marine  worms  swim  in  the  sea,  others  are 
more  or  less  closely  confined  to  their  burrows,  while  some 
form  tubes  of  sand  or  gravel  or  secrete  tubes  of  lime  which 
furnish  excellent  protection.  Such  tube-like  houses  are  often 
found  on  rocks  and  shells.  They  may  usually  be  found  on 
the  oyster  shells  in  almost  any  market.  The  part  of  the 
body  that  is  protected  has  no  further  use 
for  the  lateral  appendages  and  so  they  have 
almost  or  quite  disappeared.  On  the  head, 
however,  there  have  been  developed  great 
plume-like  appendages  which  are  well  sup- 
plied with  blood-vessels  and  act  as  gills. 
These  organs  are  often  beautifully  colored, 
and  when  fully  expanded  look  like  gorgeous 
flowers.  Indeed,  these  worms  and  the  sea- 
anemones  make  veritable  flower  gardens  in 
many  a  tide  pool  along  rocky  shores. 

The  Leeches. — In  their  general  appear- 
ance the  leeches  look  much  more  like  the  flat- 
worms  (Platyhelminthes),  than  like  the  other 
Annelida.     The  body  is  flattened,  and  com- 
FIG.     40.— The    posed  of  many  segments.     Most  of  the  seg- 

medicinal  leech,  ments  are  marked  by  transverse  lines,  making 
Hirudo  medtcina-  fU0  •  i  u 

Us.  (Grows  to  be  tne  ammal  appear  to  have  many  more  seg- 
six  or  eight  inches  ments  than  it  really  has.  The  ventral  side  is 
long>)  provided  with  two  sucking  disks.  The  mouth, 

which  lies  in  the  anterior  disk,  is  provided 
with  sharp  jaws  which  enable  the  leech  to  puncture  the  skin 
of  animals  in  order  that  it  may  suck  their  blood.  Leeches 
live  mostly  in  the  water,  and  are  found  most  commonly  on 
such  animals  as  fish,  frogs  and  others  that  are  aquatic  or 
semi-aquatic.  They  will  readily  attack  man  when  the  oppor- 
tunity offers,  and  in  olden  days  they  were  much  used  by  physi- 
cians to  "bleed"  their  patients.  A  leech  was  allowed  to  at- 


tach  itself  to  the  body  of  a  patient  and  feed  until  it  was  com- 
pletely gorged.  Leech  farms  where  these  "medicinal  leeches" 
were  raised  were  formerly  common  in  some  countries,  and  a  jar 
of  live  leeches  was  a  part  of  the  regular  stock  of  the  apothecary. 
They  are  now  seldom  used. 


CHAPTER  XV 
CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC. 

The  great  branch  Arthropoda  (Gr.  arthron,  joint;  pous, 
foot)  comprises,  as  shown  by  the  table  of  classification  on  pages 
55  t°  57>  fiye  classes;  the  Crustacea  (L.  crusta,  crust),  or 
crayfishes,  crabs,  lobsters,  barnacles,  etc.;  the  Onychophora 
(Gr.  onyx,  claw;  phero,  bear)  or  slime  slugs;  the  Myriapoda 
(Gr.  myrios,  numberless;  pous,  foot)  or  centipedes  and  thous- 
and-legged worms;  the  Arachnida  (Gr.  arachne,  spider)  or 
scorpions,  spiders,  mites  and  ticks;  and  the  Insecta 
(L.  insectum,  cut  into),  which  in  point  of  number  of  species, 
is  by  far  the  largest  class  in  the  whole  animal  kingdom. 

The  Arthropods  get  their  name  from  two  Greek  words  mean- 
ing jointed  foot,  and  the  members  of  the  branch  are  charac- 
terized by  the  possession  of  legs  and  other  laterally  arranged 
paired  appendages  each  composed  of  several  successive  jointed 
parts.  The  bodies  of  all  Arthropods  are  bilaterally  symmet- 
rical, and  are  composed,  as  are  those  of  the  Annelida,  or  an- 
nulate worms,  of  a  series  of  successive  segments.  They  are 
inclosed  by  a  more  or  less  firm  outer  cuticle,  which  not  only 
serves  as  a  protection  to  the  soft  body  parts  within  but  also 
provides  firm  points  of  attachment  for  the  muscles.  This 
hardened  cuticle  is  called  the  exoskeleton. 

The  internal  organs  of  the  Arthropods  show  a  more  or  less 
obvious  segmentation  corresponding  with  the  segmentation 
of  the  body  wall.  The  alimentary  canal  runs  longitudinally 
through  the  center  of  the  body  from  mouth  to  anal  opening- 
The  nervous  system  consists  of  a  brain  lying  above  the  esoph- 
agus and  a  double  nerve-chain  running  backward  from  the 
esophagus,  along  the  median  line  of  the  ventral  wall,  to  the  pos- 
terior extremity  of  the  body.  This  ventral  nerve-chain  con- 
sists of  a  pair  of  longitudinal-  cords  and  a  series  of  pairs  of 

1 06 


CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.  107 

ganglia,  arranged  segmentally.  The  two  ganglia  of  each  pair 
are  fused  more  or  less  nearly  completely  to  form  a  single  gang- 
lion, and  the  nerve-cords  are  partially  fused,  or  at  least  lie 
close  together.  In  addition  there  is  a  smaller  sympathetic 
system  composed  of  a  few  small  ganglia  and  certain  nerves 
running  from  them  to  the  viscera,  this  system  being  connected 
with  the  main  or  central  nervous  system.  In  this  group  the 
organs  of  special  sense  reach  for  the  first  time  a  high  stage 
of  development.  Compound  eyes  are  peculiar  to  Arthropoda. 
The  heart  lies  above  the  alimentary  canaK  Respiration  is 
carried  on  by  gills,  in  the  aquatic  forms,  and  by  a  remarkable 
system  of  air- tubes  or  tracheae  in  the  land  forms  (insects). 
The  sexes  are  usually  distinct,  and  reproduction  is  almost  uni- 
versally sexual.  Most  of  the  species  lay  eggs. 

CRUSTACEANS 

The  members  of  the  large  and  important  class  Crustacea 
are  mostly  aquatic,  but  a  few  species  are  found  on  land  in 
moist  places.  There  are  over  ten  thousand  known  species 
in  the  class,  about  nine-tenths  of  which  are  marine. 

Many  are  scavengers,  feeding  on  any  dead  organic  matter, 
and  thus  doing  a  great  service  in  helping  to  keep  the  shores, 
small  pools,  and  even  the  sea  clean.  Some  prefer  a  vegetarian 
diet  and  may  do  much  damage  to  wood  that  is  in  the  water 
or  even  to  crops  on  the  land.  The  lobsters,  crayfishes,  crabs, 
shrimps  and  prawns  furnish  man  with  an  abundant  supply  of 
most  dainty  food,  and  more  important  still,  they  furnish  an 
almost  inexhaustible  supply  of  food  to  many  other  aquatic 
animals. 

The  name  Crustacea  refers  to  the  covering  or  crust  (exo- 
skeleton)  that  protects  the  softer  parts  of  the  body  and  serves 
for  the  attachment  of  the  muscles.  This  crust  may  be  very 
hard,  as  with  the  crabs,  or  soft  and  delicate,  as  with  some  of  the 
smaller  forms. 

The  Crayfish. — The  crayfish  will  serve  as  a  typical  example 
of  the  class,  but  the  group  contains  many  remarkable  and 
important  deviations  from  the  type.  The  body  is  divided 
into  two  well  defined  regions,  the  cephalothorax  and  the  ab- 


io8    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

domen.  The  cephalothorax  is  covered  above  and  on  the  sides 
by  the  firm  carapace,  which  is  divided  by  the  transverse  cervical 
suture  into  parts  corresponding  to  the  head  and  thorax.  The 
compound  eyes  are  situated  at  the  ends  of  two  short  stalks  which 
arise  just  beneath  the  rostrum,  the  anterior  horn-like  projec- 
tion of  the  carapace.  The  segments  of  which  the  cephalo- 
thorax is  composed  are  so  fused  together  that  they  are  not 
readily  distinguished,  but  each  segment  of  the  body  bears  a 
pair  of  appendages  and  by  the  position  and  character  of  these 
appendages  the  different  regions  can  be  determined.  Each 
of  these  appendages,  except  the  antennae,  consists  of  a  basal 
part  from  which  arises  two  branches  made  up  of  one  or  more 
segments  modified  to  perform  certain  functions. 

Just  below  the  eyes  is  the  first  pair  of  appendages,  the 
antennules,  in  the  base  of  each  of  which  is  an  organ  formerly 
supposed  to  be  an  auditory  organ  but  now  known  to  be  an 
organ  of  equilibration.  These  aid  the  animal  in  keeping  the 
body  in  a  proper  position  while  swimming.  Next  come  the 
antenna,  or  feelers,  which,  like  the  antennules,  are  provided 
with  fine  hairs  which  aid  in  the  sense  of  touch  and  perhaps  of 
smell.  The  green  gland  lies  at  the  base  of  the  antennas.  It  is 
probably  an  excretory  organ  with  functions  similar  to  the 
kidneys  of  higher  animals. 

Next  comes  the  group  of  appendages  surrounding  the  mouth, 
the  mandibles,  two  pairs  of  maxilla  and  three  pairs  oimaxilli- 
peds.  The  mandibles  are  hard  and  jaw-like.  The  second 
maxillae  have  a  large  paddle-like  structure,  the  scaphognathite, 
which  extends  back  over  the  gills  in  the  branchial  chamber, 
the  space  between  the  lower  part  of  the  carapace  and  the  body- 
wall.  The  movements  of  this  appendage  keep  the  currents  of 
water  flowing  through  the  gill  chamber.  The  maxillipeds  are 
appendages  of  the  thorax.  The  first  pair  of  legs  is  much 
larger  than  the  others,  the  terminal  segments  being  developed 
into  strong  pincers  or  chela.  Each  pair  of  legs,  except  the 
last,  bears  gills  which  extend  up  into  the  branchial  chamber. 
In  the  basal  segments  of  the  last  pair  of  legs  of  the  male  are  the 
genital  pores.  In  the  female  the  genital  pores  are  in  the 
basal  segments  of  the  second  pair  of  walking-legs.  In  the 


CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.    109 


antennule 


opening  of  green  gland 


-uropod 
-telson 


FIG.  41. — Ventral   aspect  of  female  crayfish,    Cambarus  sp.,   with  the 
appendages  of  one  side  removed. 


no    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

male  each  segment  of  the  abdomen,  except  the  last,  bears  a 
pair  of  appendages  or  swimmerets.  The  first  two  pairs  are 
modified  to  serve  as  channels  for  the  sperm  fluid.  The  last 
pair  of  appendages  is  broad  and  flat  and  with  the  last  segment, 
the  telson,  forms  the  broad  tail,  or  swimming  fin.  In  the 
female  the  first  two  pairs  of  abdominal  appendages  are  very 
small  or  altogether  lacking. 

The  food,  which  for  the  most  part  consists  of  vegetable 
matter,  or  dead  organic  matter,  passes  into  the  stomach 
through  a  short  esophagus.  The  stomach  is  divided  into  two 
parts.  The  anterior  portion,  the  cardiac  chamber,  contains 
three  strong  teeth,  the  gastric  mill.  These  grind  the  food 
before  it  passes  back  through  a  fine  strainer  of  stiff  hairs  into 
the  second  or  pyloric  chamber,  which  receives  the  secretions 
from  the  large  digestive  glands  that  surround  the  stomach. 
The  intestine  is  a  straight  tube  opening  to  the  outside  by  a 
slit-like  anal  opening  on  the  under  side  of  the  telson. 

The  heart  lies  in  the  pericardial  sinus  in  the  posterior 
portion  of  the  cephalothorax.  The  contractions  of  the  heart 
force  the  blood  out  into  seven  arteries  which  carry  it  to  all 
parts  of  the  body.  The  ophthalmic  artery  supplies  the  eyes 
and  other  parts  of  the  head.  The  two  antennary  arteries 
supply  the  antennae,  excretory  organs  and  other  tissues.  The 
two  hepatic  arteries  supply  the  digestive  glands.  The  dorsal 
abdominal  artery  supplies  the  intestine  and  surrounding 
tissues.  The  sternal  artery  passes  down  to  the  ventral  wall 
where  it  divides,  one  part  carrying  blood  to  the  appendages  in 
the  thorax  and  the  other  part  to  the  appendages  of  the  abdo- 
men. All  of  the  arteries  give  off  many  branches  which  divide 
again  and  again  into  very  small  capillaries  which  open  into 
spaces  between  the  tissues.  From  all  of  the  tissues  the  blood 
finally  makes  its  way  to  a  large  space,  the  sternal  sinus,  in  the 
ventral  part  of  the  thorax.  From  the  sinus  it  passes  out  into 
channels  in  the  gills  where  it  gives  off  its  carbon  dioxide  and 
receives  oxygen  from  the  water  which  bathes  the  gills.  Then 
through  other  channels,  the  branchio-cardiac  sinuses,  it 
reaches  the  pericardial  sinus  which  surrounds  the  heart. 
From  here  it  enters  the  heart  through  three  pairs  of  openings, 


CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.  in 


the  ostia,  which  are  guarded  by  valves  that  allow  the  blood  to 
enter  but  prevent  it  from  flowing  back  into  the  sinus. 

The  nervous  system  is  similar  to  that  of  the  earthworm  and 
the  insects.  It  consists  of  a  dorsal  ganglionic  mass,  the  brain, 
which  is  connected  by  cords  passing  around  the  esophagus 
with  the  ventral  nerve  cord  which  lies  along  the  floor  of  the 
thorax  and  abdomen.  Along  the  ventral  nerve  cord  are  a 
number  of  ganglia  which  give  off  nerve  fibers  that  reach  the 
various  parts  of  the  body. 

The  abdomen  is  quite  filled  with  the  powerful  muscles  that 
flex  that  part  of  the  body  forward  when  the  crayfish  is  swim- 
ming, thus  producing  backward  locomotion.  These  muscles, 
as  well  as  the  strong  muscles  of  the  appendages,  are  all  at- 
tached to  the  firm  body-wall,  or  exoskeleton,  not  to  an 
internal  skeleton  as  in  the  vertebrates. 

The  sexes  are  separated.  The  spermatozoa  are  produced  in 
the  male  in  the  tri-lobed  testis  which  lies  under  the  heart  and 
over  the  anterior  end  of  the  intestine.  They  pass  through  the 
long,  coiled,  paired  vasa  defer  entia  to  the  genital  apertures  in  the 
base  of  the  last  pair  of  thoracic  legs.  The  eggs  arise  in  the 
bilobed  ovary  in  the  female  and  pass  through  the  paired  ovi- 
ducts and  out  through  the  genital  apertures  on  the  next  to  the 
last  pair  of  thoracic  legs.  The  eggs  are  glued  to  the  swimmerets 
of  the  female,  and  remain  in  this  position  until  they  hatch. 

During  the  very  early  part  of  their  development  the  young 
or  larval  crayfish  cling  to  the  old  egg  shells  or  to  the  spinnerets 
of  their  mother  thus  receiving  much  needed  protection,  for 
their  bodies  are  very  soft.  After  about  two  days  the  young 
make  their  first  moult,  casting  off  the  old  skin  after  a  new  one 
has  been  formed  underneath  it.  They  usually  moult  about 
seven  times  during  the  first  summer  and  grow  very  rapidly 
after  each  moult.  In  the  process  of  moulting  the  lining  of  the 
esophagus,  stomach  and  the  alimentary  canal  is  also  cast  off. 
Often  one  or  more  of  the  appendages  may  be  lost  during 
moulting.  Such  lost  parts  are  usually  regenerated  and  it  is 
not  uncommon  to  find  individuals  with  one  of  the  claws  or 
legs  shorter  than  the  others,  the  short  appendage  being  a  new 
one  that  is  replacing  one  that  has  been  lost. 


CRAYFISH,  LOBSTERS,   CRABS,  SHRIMPS,  ETC.  113 

Crayfish,  or  crawfish,  as  they  are  more  commonly  called, 
are  found  in  most  fresh  water  ponds  and  streams.  The 
common  species  in  the  eastern  United  States  belong  to  the 
genus  Cambarus,  those  on  the  Pacific  Coast  to  the  genus  Astacus. 
Some  species  live  in  holes  in  the  ground,  digging  deep  enough 
to  reach  water,  or  at  least  considerable  moisture.  The  earth 
that  is  removed  in  digging  the  burrows  is  sometimes  built  up 
to  form  short  chimneys  above  the  ground.  This  burrowing 
habit  is  often  the  cause  of  serious  damage  to  the  levees  along 
the  rivers,  particularly  along  the  Mississippi  River.  In  the 
southern  United  States  crayfish  often  occur  in  such 
numbers  that  they  become  important  pests  in  the  corn  and 
cotton  fields.  In  badly  infested  areas  there  may  be  as  many 
as  10,000  or  12,000  holes  to  the  acre.  From  these  holes  the 
crayfish  issue  in  the  evenings  or  on  rainy  mornings  and  feed 
on  the  young  tender  plants.  They  may  be  easily  killed  by 
placing  a  little  carbon  bisulphid  in  each  hole. 

In  some  sections  of  the  country  crayfish  are  used  for  food 
and  are  considered  a  great  delicacy,  those  on  the  west  coast,  on 
account  of  their  size,  being  particularly  in  demand.  Recent 
attempts  have  been  made  to  introduce  these  larger  species 
into  waters  where  only  the  smaller  ones  occur  naturally. 
In  Europe  the  crayfish  have  been  used  for  food  for  centuries 
and  in  France  "crayfish  farming"  has  been  successfully 
practiced  for  many  years. 

CLASSIFICATION 

The  class  Crustacea  is  divided  into  two  sub-classes,  the 
Entomostraca  and  the  Malacostraca. 

Sub-ckss  Entomostraca. — Entomostraca  are  mostly  small, 
comparatively  simple  forms  with  little  differentiation  of  the 
appendages.  Four  orders  are  included  in  this  class.  The 
order  Phyllopoda  comprises  mostly  fresh  water  species  with 
leaf-like  appendages.  The  "  fairy  shrimps,  "  common  in  fresh 
water  pools  in  the  early  spring,  are  among  the  largest  examples. 
The  species  of  A  rtemia,  an  abundant  Phyllopodin  salt  and  brack- 
ish or  fresh  water,  are  of  great  interest  to  biologists  on  account 


ii4    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


of  the  changes  that  may  take  place  in  them  when  the  density  of 
the  water  is  changed.  Artemia  and  several  other  genera  be- 
longing to  this  order  form  a  very  important  food  supply  for 
many  fishes. 

To  the  order  Ostracoda  belong  several  genera;  Cypris,  which 
occurs  in  fresh  water,  and  Cypridina,  which  is  marine,  are  the 
most  common.  These  resemble  minute  bivalve  shells  and 
often  occur  in  great  numbers  near  the  surface  where  the 
surface-haunting  fish  and  other  animals  feed  on  them. 

In  the  order  Copepoda  the  body  is 
long  and  distinctly  segmented,  and  the 
appendages  are  confined  to  the  head 
and  thorax.  The  water-fleas,  Cyclops, 
are  common  in  all  pools  or  quiet  waters. 
The  single  median  eye  has  suggested 
the  generic  name.  These  are  often  used 
as  examples  to  show  how  rapidly  some 
of  these  forms  may  multiply.  It  has 
been  estimated  that  the  descendants 
of  a  single  individual  might  in  one 
year  number  nearly  4,500,000,000,  if  all 
the  young  lived  and  produced  their  full 
number  of  offspring.  They  feed  on 
other  smaller  animals  such  as  Protozoa 
and  Rotifera,  and  in  turn  serve  as  one 
of  the  most  important  sources  of  food 
for  the  young  of  many  fresh  water  fishes.  Related  to  Cyclops 
is  the  genus  Cetochilus  which  occurs  in  the  surface  water  of 
the  sea  in  inconceivable  numbers,  sometimes  forming  almost  a 
solid  mass  extending  for  miles  in  quiet  waters.  Those  whales 
which  are  furnished  with  fringes  of  whalebone  in  the  mouth 
often  swim  in  schools  through  the  water  where  these  minute 
creatures  abound,  and  as  the  water  rushes  through  the  wide- 
open  mouth  the  minute  crustaceans  are  strained  out  and 
thus  furnish  a  dainty  and  abundant  supply  of  food  for  the 
largest  of  living  animals.  To  the  genus  Sapphirina  belong 
some  of  the  most  wonderfully  phosphorescent  animals  that 
are  found  in  the  sea.  This  order  also  includes  the  so-called 


FIG.  43. — Water-flea, 
Cyclops,  female  with 
egg  masses.  (From  life, 
greatly  magnified.) 


CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.  115 


fish-lice  which  are  especially  interesting  because  of  their 
parasitic  habits  and  the  greatly  modified  structure  resulting 
therefrom.  Some  live  as  commensals,  that  is,  are  associated 
with  their  hosts  in  such  a  way  as  to  derive  benefit  from  them, 
without  injuring  them.  Others  are  truly  parasitic  and  live 
upon  the  blood  or  tissues  of  their  host.  The  most  common  of 
these  attach  themselves  to  the  gills  of  fishes,  but  they  may  also 
be  found  as  external  or  internal  parasites,  of  whales,  molluscs, 
marine  worms,  starfishes  and  many  other  animals  that  are 
found  in  the  sea. 

The  barnacles,  order  Cirripedia,  look  but  little  like  other 
Crustacea.  For  a  long  while  they  were  classed  with  the 
Molluscs,  but  a  study  of  their 
development  showed  that  in  the 
young  stages  they  are  like  the 
crustaceans  and  not  the  molluscs. 
The  young  are  free-swimming, 
and  after  going  through  a  series 
of  changes  they  become  attach- 
ed to  some  firm  object.  Here 
the  young  barnacle  undergoes 
further  metamorphosis,  and  the 
adult  form  with  its  compact  or 
somewhat  worm-like  body  is  de- 
veloped. The  appendages,  or 
legs,  are  long,  slender  and  curled. 
The  animal  is  enclosed  in  a  shell 
often  of  the  shape  of  a  truncate 


FIG.  44. — A  stalked  barnacle, 
Lepas  hillii.  (About  |  natural 
size.) 


cone  and  composed  of  six  or  more  plates.  The  open  end  of 
the  shell  may  be  closed  by  a  lid  or  operculum,  thus  well  pro- 
tecting the  inmate.  The  barnacle  feeds  on  minute  organisms 
which  it  sweeps  into  its  mouth  by  means  of  the  long  feathery 
appendages. 

Although  barnacles  may  completely  cover  piling  and  other 
timbers  in  the  water,  they  do  not  injure  them  and  may  even 
be  of  some  service  in  protecting  them  from  wood-boring  or 
wood-destroying  animals.  Sometimes,  however,  they  are 
serious  pests  on  oyster  beds.  The  goose-barnacle,  or  ship- 


barnacle,  is  attached  to  floating  objects  by  means  of  a  flexi- 
ble stalk  which  may  be  very  short  or  may  attain  a  length  of 
nearly  a  foot.  In  warm  seas  the  bottoms  of  ships  are  often 
so  covered  with  these  barnacles  that  their  progress  is 
seriously  impeded. 

The  very  degenerate  parasitic  Sacculina  also  belongs  to  this 
order.  The  young  sacculina  swims  about  freely,  but  soon 
attaches  itself  to  the  body  of  a  crab.  After  undergoing  a 
series  of  changes,  one  stage  of  which  is  passed  within  the  body 
of  the  crab,  it  finally  becomes  little  more  than  an  ovoid  sack 
closely  applied  to  the  host,  and  sending  off  many  root-like 
filaments  which  extend  to  all  of  the  tissues  of  the  crab  from 
which  it  derives  its  nourishment. 

Sub-class  Malacostraca. — This  group  includes  the  more 
highly  organized  Crustacea.  Most  of  them  are  of  considerable 
size,  and  the  appendages  show  much  differentiation.  There 
are  several  orders,  some  including  mostly  fresh  water,  others 
mostly  marine  forms,  but  the  members  of  only  two  of  these 
orders  are  of  any  particular  economic  interest  or  importance 
except  as  they  furnish  food  for  fishes  and  other  smaller  animals. 

The  order  Decapoda,  to  which  the  crayfish  belongs,  is  the 
largest  and  most  important  order  belonging  to  the  class.  The 
order  is  divided  into  two  groups,  or  sub-orders,  the  Macrura 
and  the  Brachyura.  In  the  Brachyura  the  abdomen  is  usually 
much  reduced  in  size  and  folded  underneath  the  thorax. 
The  Macrura  includes  the  free-swimming  shrimps  and  prawns, 
the  crawling  lobsters  and  crayfish,  and  the  hermit  crabs,  sand 
bugs  and  others. 

Lobsters. — As  a  source  of  food  for  man  the  lobsters  rank 
first  among  the  Crustaceans.  They  are  found  along  rocky 
shores  on  both  sides  of  the  Atlantic  ocean.  In  structure  and 
habits  they  are  much  like  the  crayfish,  but  they  attain  a  much 
greater  size,  some  individuals  reaching  a  length  of  twenty  inches 
and  a  weight  of  twenty-five  pounds.  At  rare  intervals  even 
larger  specimens  are  found,  but  these  are  to  be  regarded  as 
giants.  The  lobsters  seen  in  the  market  usually  measure  ten 
to  twelve  inches  and  weigh  from  one  and  one-half  to  two  and 
one-half  pounds.  Many  states  do  not  allow  lobsters  to  be 


CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.  117 

taken  that  are  less  than  nine  inches  long;  others  place  the 
minimum  at  ten  or  ten  and  one-half  inches. 

The  food  of  lobsters  consists  of  fish  and  any  other  animals 
that  they  can  capture  in  the  sea.  Although  they  prefer  fresh 
food  they  do  not  hesitate  to  eat  dead  or  even  decomposing 
animal  matter. 

Females  eight  or  ten  inches  long  may  produce  5000  to  10,000 
eggs.  Very  large  lobsters  may  produce  nearly  ten  times  this 
number.  The  eggs  are  glued  to  the  swimmerets  and  thus 
protected  as  are  the  eggs  of  the  crayfish. 

Live  lobsters  are  brownish  or  greenish  with  bluish  mottlings. 
The  ones  usually  seen  in  the  market  are  red  because  they  have 
been  boiled. 

At  one  time  lobsters  were  very  plentiful  and  very  cheap 
along  the  New  England  and  Canadian  coasts.  It  was  no 
uncommon  thing  for  as  many  as  100,000,000  to  be  marketed 
in  a  year,  and  the  price  was  often  as  low  as  five  cents  for  a 
large  lobster.  But  for  the  last  thirty  years  the  numbers  have 
been  decreasing  very  rapidly  until  now  the  catch  is  only  a 
small  fraction  of  what  it  used  to  be,  possibly  little  more  than 
one-tenth,  and  many  of  the  best  grounds  are  no  longer  fished 
because  they  do  not  yield  profitable  returns.  As  the  supply 
decreased  the  prices  rapidly  increased  until  now  in  many 
places  lobsters  sell  from  fifty  cents  to  one  dollar  each.  The 
problem  of  how  to  conserve  the  supply  that  still  exists  is  a 
very  important  one  and  has  been  the  subject  of  much  study  and 
experimenting.  Closed  seasons  and  a  gauge  or  length  limit 
have  been  tried.  "Egg-lobster"  laws  have  been  passed  for 
the  protection  of  the  female  during  the  time  she  is  carrying 
her  eggs.  But  there  has  been  only  a  partial  check  in  the 
destruction  of  the  industry.  With  certain  modifications  of 
these  laws  and  with  the  methods  of  artificial  propagation  that 
are  now  being  practiced  in  some  states,  it  is  hoped  that  more 
encouraging  results  may  be  met  with.  The  lobster  fisheries 
on  the  seacoasts  of  Europe  have  had  the  same  difficulties 
that  have  been  met  with  here. 

The  common  American  lobster  is  called  Homarus  americanus , 
and  the  common  lobster  of  Europe  H.  grammarus,  the  Nor- 


n8    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

wegian  lobster,  Nephrops  norwegicus.  Around  the  islands  off 
the  coast  of  California  is  a  large  crustacean  about  the  size  of 
the  eastern  lobster,  but  the  front  legs  are  not  enlarged 
into  the  great  heavy  pincers.  It  is  often  referred  to  as  the 
spiny  lobster,  or  "salt  water  crawfish."  It  belongs  to  the 
genus  Palinurus,  which  is  represented  in  different  parts  of  the 
world  by  several  species  that  are  highly  valued  as  food. 

Shrimps  and  Prawns. — The  prawns,  which  are  marine  and 
much  like  the  lobsters  but  very  much  smaller,  and  the  shrimps, 
which  occur  in  both  fresh  and  salt  water,  are  often  much  sought 
after  for  food.  They  often  occur  in  great  "schools,"  and  are 
caught  in  nets  or  dredges,  sometimes  in  great  numbers.  They 
are  put  fresh  directly  on  the  market,  or  are  canned  and 
shipped  to  all  parts  of  the  world.  The  principal  shrimp  fish- 
eries are  along  the  shores  of  the  Gulf  of  Mexico  where  the 
common  shrimp,  Crangon  vulgaris,  is  exceedingly  abundant. 
Most  of  the  canned  shrimp  come  from  this  region.  The  same 
species  occurs  on  the  Pacific  coast  where,  however,  the  Cali- 
fornia shrimp,  C.  franciscorum,  is  more  important.  Besides 
supplying  the  local  markets  with  the  fresh  shrimp  the  California 
Chinese  formerly  dried  great  quantities  of  them.  The  dried 
meat  was  separated  from  the  shell  and  exported,  the  value 
of  the  export  reaching  $100,000,  in  some  seasons. 

Some  of  the  largest  and  finest  prawns  and  shrimps  are 
found  in  Puget  Sound,  but  the  demand  for  them  is  so  great 
that  they  seldom  get  beyond  the  local  market.  Like  the 
lobster  fisheries,  the  shrimp  fisheries  have  suffered  from  lack 
of  intelligent  regulation. 

It  should  be  noted  that  these  crustaceans,  which  occur  in 
untold  numbers  in  so  many  waters,  form  a  large  part  of  the 
food  supply  of  many  of  our  important  food  fishes,  and  the 
destruction  or  material  reduction  of  this  source  of  food  has 
an  effect  more  far-reaching  than  at  first  appears. 

The  hermit  crabs,  which  are  more  nearly  related  to  the 
shrimps  and  prawns  than  to  the  true  crabs,  found  along  all 
seashores,  well  illustrate  the  structural  changes  that  may  be 
brought  about  by  a  special  or  peculiar  mode  of  life.  Very  early 
the  young  animals  seek  out  an  empty  shell,  such  as  a  snail  or 


CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.    119 

periwinkle  shell,  in  which  they  may  hide.  The  body  is  thrust 
well  into  the  shell  and  the  opening  guarded  by  the  feet  and  claws. 
As  the  crab  develops  it  becomes  more  and  more  adapted  to  the 
shell  in  which  it  is  living.  The  abdomen  remains  soft  and 
follows  the  convolutions  of  the  shell.  Only  the  last  two 
abdominal  appendages  remain,  and  these  are  modified  into 
hook-like  organs.  The  first  two  or  three  pairs  of  thoracic  legs 


FIG.  45. — A  hermit  crab,  Pagarus  sp.  in  a  sea-snail  shell.     Upper  figure 
shows  another  crab  removed  from  its  shell.     (Reduced.) 


become  curiously  modified  and  help  close  the  opening  of  the 
shell.  The  right  claw  is  often  very  much  larger  than  the  left 
and  well  fitted  for  the  dual  purpose  of  capturing  prey  and 
acting  as  a  door.  As  the  crab  grows,  its  adopted  home  be- 
comes too  small  for  it,  and  from  time  to  time  it  must  seek 
larger  shells. 

Some  of    the  hermit  crabs   always  have   certain  stinging 


120    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

hydroids  or  sea-anemones  attached  to  their  shells.  Both 
animals  doubtless  derive  some  benefit  from  this  association, 
the  crab  being  protected  from  its  enemies  and  the  hydroid  or 
anemone  being  moved  from  place  to  place  where  food  is  more 
abundant  and  perhaps  gathering  some  of  the  bits  that  are 
scattered  in  the  water  when  the  crab  is  feeding.  This  is 
another  example  of  commensalism,  or  symbiosis. 

The  sand-bugs,  genus  Hippa,  so  numerous  on  sandy  beaches, 
burrowing  rapidly  into  the  loose  sands  or  sometimes  swimming 
about  in  the  tide  pools,  are  an  important  source  of  food  for 
some  fish. 

Many  other  interesting  forms  in  this  sub-order,  some  of  them 
of  more  or  less  economic  importance,  might  be  listed,  but  the 
kinds  already  mentioned  serve  to  show  something  of  the 
diversity  of  structure  and  habits  of  the  group. 

Crabs. — The  true  crabs,  belonging  to  the  sub-order  Brachy- 
ura,  differ  from  the  crayfish  and  lobsters  in  having  the  body 
short  and  broad  instead  of  elongate  and  rounded.  The 
cephalothorax  is  often  broader  than  long.  The  abdomen  is 
relatively  small  and  is  bent  under  the  cephalothorax  so  that  but 
little  of  it  is  visible  from  above.  The  appendages  are  usually 
well  developed  and  similar  to  those  of  the  crayfish  or  lobster 
except  that  the  number  of  abdominal  appendages  is  reduced 
to  two  pairs  in  the  male  and  four  pairs  in  the  female.  Most 
crabs  are  scavengers,  living  on  dead  animal  matter.  During 
their  development  they  undergo  a  remarkable  metamorphosis. 
In  some  of  these  stages  they  are  so  unlike  the  adult  that  they 
were  described  as  different  animals.  The  names,  such  as 
zoea  and  megalops,  given  to  these  supposedly  distinct  animals, 
are  still  retained,  but  we  know  now  that  they  refer  to  different 
stages  in  the  development  of  the  crab. 

Most  of  the  crabs  live  in  the  shallow  waters  near  the  shore, 
but  some  live  in  deep  water  and  a  few  live  on  land.  Their 
habits  are  various  and  there  is  a  corresponding  variation  in 
their  structure  and  shape,  size  and  coloring. 

The  spider  crabs,  with  their  long,  slender  legs  and  com- 
paratively small  body,  are  especially  strange  looking  creatures. 
Some  members  of  this  group  living  in  Japanese  waters  measure 


CRAYFISH,  LOBSTERS,  CRABS,  SHRIMPS,  ETC.  121 

twelve  to  sixteen  feet  across  the  extended  legs,  the  body  itself 
being  but  little  more  than  a  foot  in  width  or  length. 

The  fiddler  crabs,  Uca  spp.,  so  common  along  the  Atlantic 
coast,  are  the  clowns  among  the  crabs.  The  males  have  one 
of  the  chelae  very  much  enlarged,  and  when  alarmed  they 
move  this  swiftly  back  and  forth  with  a  motion  ridiculously 
like  that  of  a  violinist  with  his  bow. 

The  blue  crab,  or  "soft-shelled"  crab,  Callinectes  hastatus, 
is  the  most  important  as  a  source  of  food  on  the  Atlantic 
coast.  On  the  Pacific  Coast  a  much  larger  crab,  Cancer 
magister,  is  taken  in  shallow  waters,  sometimes  in  considerable 
numbers,  and  is  much  prized. 

The  horseshoe  crab,  or  king-crab,  Litmdus,  common  all  along 
the  Atlantic  coast,  is  really  not  a  crab  at  all,  nor  even  a  crus- 
tacean, but  belongs  to  another  class, 
the   relationship  which  is  uncertain. 
Many  believe  that  Limulus  is   most 
nearly  related  to  the  spiders. 

The  beach  fleas,  order  Amphipoda, 
are  perhaps  the  most  numerous  crus- 
taceans found  on  the  sea  beaches,  oc- 
curring in  countless  numbers  in  the 
tossed  up  seaweeds  and  mosses  and 
other  sea  wrack.  They  are  important 
as  food  for  other  marine  animals.  The 
boring  Amphipod,  genus  Chelura, 
works  on  submerged  timber,  often 
doing  a  great  deal  of  damage. 

The  wood-lice  or  sow-bugs,  order  mined. 
Isopoda,  are  among  the  few  crus- 
taceans that  live  a  wholly  terrestrial  life.  They  live  in  moist 
places,  feeding  chiefly  on  decaying  vegetable  matter,  but 
sometimes  attacking  tender  plants  and  doing  more  or  less 
damage  in  gardens  and  green-houses.  Although  land  animals, 
they  breathe  by  means  of  gills  which  are  situated  on  the  under 
side  of  the  abdomen.  It  is  therefore  necessary  for  them  to 
live  in  places  where  the  gills  may  be  kept  damp  in  order  that 
there  may  be  a  ready  transfer  of  gases  through  the  membranes. 


122    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Their  breeding  or  hiding  places  are  usually  easily  found  and 
destroyed,  or  sliced  potatoes  or  substances  poisoned  with 
Paris  green  may  be  placed  where  the  sow-bugs  can  find  them. 
Some  members  of  this  same  order  live  in  fresh  water,  others 
are  marine. 

The  gribbles,  genus  Limnoria,  are  another  group  of  crus- 
taceans that  are  very  destructive  to  piles  and  other  submerged 
woods,  which  they  may  completely  honeycomb  to  the  depth  of 
half  an  inch  or  more.  Where  abundant  they  may  cause  the 
piles  to  lose  as  much  as  an  inch  of  surface  each  year.  It  is  a 
common  practice  now  to  give  the  piles  a  coat  of  creosote,  or 
better  still  to  drive  the  creosote  into  the  wood  by  pressure,  in 
order  to  protect  it  from  the  ravages  of  these  and  other  wood 
boring  species.  These  gribbles  attack  and  destroy  much 
floating  and  water-logged  timber  that  might  otherwise  become 
serious  obstructions  to  navigation. 


CHAPTER  XVI 


SLIME   SLUGS,   MYRIAPODS   AND   INSECTS 

Slime  Slugs. — The  slime  slugs,  composing  the  small  class 
Onychophora  of  the  great  branch  Arthropoda,  are  curious,  soft- 
bodied,  many-legged,  but  sluggish  creatures 
about  two  inches  long,  that  live  under  bark  or 
stones  mostly  in  sub-tropic  and  tropic  lands. 
About  fifty  species  of  them  are  known.  The 
best  known  genus  is  named  Peripatus.  They 
capture  small  insects  for  food  by  ejecting  slime 
on  them  from  glands  in  the  mouth.  Their 
bodies  show  a  curious  combination  of  worm 
character  and  arthropod  characters.  The  ani- 
mals really  seem  to  be  a  sort  of  link  between  the 
Annelida  and  the  Arthropoda. 

Myriapods. — The  class  Myriapoda1  includes 
the  familiar  thousand-legged  or  galley  worms 
and  centipedes  as  well  as  certain  smaller  crea- 
tures bearing  only  a  few  pairs  of  legs.  They 
are  land  animals,  and  have  the  body  segments 
nearly  uniform  in  size  and  shape,  except  the 
head  which  bears  the  mouth-parts  and  antennas. 
The  presence  of  true  legs  on  most  of  the  seg- 
ments of  the  hinder  part  of  the  body  and  the 
lack  of  the  grouping  of  these  segments  into 
distinct  thorax  and  abdomen  are  the  further 
external  structural  characteristics  which  distin- 
guish myriapods  from  insects.  The  internal 
anatomy  corresponds  in  general  character  with 
that  of  the  Insecta. 

1  Modern  classification  tends  to  discard  the  long  recognized  class 
Myriapoda  in  favor  of  two  classes,  one  for  the  centipedes  and  allies,  and 
the  other  for  the  thousand-legged  worms  and  allies. 

123 


FIG.  47.— 
Peripatus  ei- 
seni  (Mex- 
ico). (Length 

tw° 


i24    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  most  familiar  myriapods  are  the  millipeds  or  galley 
worms,  the  centipedes,  geophilids,  and  lithobians.  The  milli- 
peds are  cylindrical  in  shape,  have  two  pairs  of  legs  on  most 
of  the  body-segments  and  are  vegetable  feeders,  though  some 
may  feed  on  dead  animal  matter.  The  galley-worms,  Julus 
spp.,  large,  blackish,  cylindrical  millipeds  found  under  stones 
and  logs  and  leaves  in  loose  soil,  are  familiar  forms.  They 
crawl  slowly,  and  when  disturbed  curl  up  and  emit  a  mal- 
odorous fluid.  They  can  easily  be  kept  alive  in  shallow  glass 
vessels  with  a  layer  of  earth  in  the  bottom,  and  their  habits 


FIG.  48. — A  milliped,  Julus  sp.     (Natural  size.) 

and  life  history  may  thus  be  studied.  They  should  be  fed 
sliced  apples,  green  leaves,  grass,  strawberries,  fresh  ears  of 
corn,  etc.  They  are  not  poisonous  and  may  be  handled  with 
impunity.  They  lay  their  eggs  in  little  spherical  cells  or  nests 
in  the  ground.  An  English  species,  of  which  the  life  history 
has  been  studied,  lays  from  60  to  100  eggs  at  a  time.  The 
eggs  of  this  species  hatch  in  about  12  days. 

The  lithobians,  centipedes  and  geophilids  are  flattened  and 
have  but  a  single  pair  of  legs  on  each  body-ring.  They  are 
predaceous  in  habit,  catching  and  killing  insects,  snails,  earth- 
worms, etc.  They  can  run  rapidly,  and  have  the  first  pair 
of  legs  modified  into  a  pair  of  poison  claws,  which  are  bent 
forward  so  as  to  lie  near  the  mouth.  The  common  "skein" 
centipede,  Scutigera  forceps,  is  yellowish  and  has  fifteen  pairs 
of  legs,  long  4o-segmented  antennae,  and  nine  large  and  six 
smaller  dorsal  segmental  plates.  The  true  centipedes,  Scolo- 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS    125 


pendra  spp.,   have   twenty-one   to   twenty-three  body-rings, 

each  \vith  a  pair  of  legs,  and  the  antennae  have  seventeen  to 

twenty  joints.     They  live  in  warm  regions,  some  growing  to 

be  as  long  as  twelve  inches  or  more.     The  "bite"  or  wound 

made  by  the  poison  claws  is  fatal  to  insects  and  other  small 

animals,  their  prey,  and  painful  or  even  dangerous  to  man. 

The  popular  notion  that  a  centipede 

"stings"  with  all  of  its  feet  is  falla- 

cious.    It   is   recorded  by  Humboldt 

that  centipedes  are  eaten  by  some  of 

the   South    American    Indians.     The 

geophilids  are  very  slender-bodied  and 

usually    rather     long     centipede-like 

forms  with  as  many  as  300  pairs  of 

legs.    They  are  usually  yellowish  and 

are   common  in   damp    places   under 

stones  or  logs,  or  in  the  ground. 

Insects 

The  great  class  Insecta,  with  its 
350,000  known  species,  is  a  group  of 
animals  of  special  importance  in  the 
study  of  economic  zoology.  As  we 
know  but  few  more  than  500,000 
different  kinds  of  animals  altogether, 
it  is  apparent  how  dominant  among 
animals,  as  regards  numbers  at  least, 
the  insects  are.  In  fact  we  might 

well  call  this  the  Age  of  Man  and  „    , 

...  .    .,       ..,     ,,  ,.       scolo  pendra  sp.     (.Natural 

Insects,  to  contrast  it  with  the  earlier  size  ^ 

Age  of  Reptiles,  Age  of  Fishes,  Age 

of  Invertebrates,  etc.  The  insects  include  more  kinds  of 
animals  directly  injurious  to  the  material  welfare  of  man 
and  to  his  health  and  duration  of  life  than  any  other  animal 
group.  So  it  is  that  as  students  of  economic  zoology  we 
must  give  insects,  and  their  relations  to  man,  a  more  detailed 
consideration  than  we  shall  give  any  other  animals. 


FIG-  49-—  A   centipede 


i26    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Although  from  the  silk- worm  we  get  all  the  silken  cloth  and 
thread  we  use,  and  from  the  honey-bee  all  the  honey  and 
beeswax,  yet  these  are  almost  the  only  species  of  insects  of  all 
the  myriad  living  kinds  that  afford  man  useful  products. 
But  in  two  other  and  far  more  important  ways,  insects  are  of 
direct  benefit  to  us.  Some  of  them  act  as  scavengers  of  con- 
siderable importance,  and  many  of  them  kill  injurious  species 
of  their  own  class.  It  is,  indeed,  on  the  many  predaceous  and 
parasitic  insects  that  we  rely  for  chief  protection  from  the 
many  injurious  and  dangerous  kinds.  We  can,  and  do, 
make  much  headway  against  injurious  insects  by  the  use 
of  artificial  remedies,  but  without  natural  checks  on  their 
increase,  among  which  checks  the  attacks  of  other  insect 
species  are  the  most  important,  insect  pests  would  overrun  us 
completely. 

A  knowledge  of  the  special  structure,  physiology  and  mode  of 
development  of  insects  is  necessary  as  a  basis  for  good  work  in 
economic  or  applied  entomology.  And  a  knowledge  of  insect 
classification,  which  of  course  is  based  on  similarities  and 
dissimilarities  both  of  structure  and  of  development  and  habit, 
and  which  indicates  by  a  few  words  the  existence  of  these 
resemblances  and  differences,  is  also  most  important  to  the 
economic  entomologist.  Hence  our  first  consideration  of 
insects  will  concern  itself  with  their  structure,  physiology, 
development  and  classification.  The  study  of  the  grasshop- 
per, already  made,  has  given  us  a  good  understanding  of  the 
insect  body.  But  there  is  much  modification,  or  specialization, 
of  general  body-shape  and  character  as  well  as  of  the  various 
particular  parts  of  it,  as  antennae,  mouth-parts,  legs,  wings, 
etc.,  and  it  will  be  advisable  to  examine  in  some  detail  the 
external  features  of  the  body  of  a  highly  specialized  insect 
such  as  the  honey-bee.  A  number  of  statements  concerning 
the  general  make-up  of  the  insect  body,  already  made  in  con- 
nection with  the  study  of  the  grasshopper,  will  be  repeated  and 
expanded  and  a  number  of  technical  names  of  parts  of  the 
body  redefined.  The  grasshopper  was  studied  primarily  as 
an  introduction  to  the  invertebrates  in  general.  The  bee  will 
be  studied  primarily  as  an  introduction  to  the  insects. 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS    127 

THE  EXTERNAL  STRUCTURE  or  THE  HONEY-BEE 

Body -wall. — The  body  of  a  bee,  which  is  a  well-developed 
insect  type,  is,  let  us  note  first  of  all,  entirely  covered  by  a  firm 
body  wall  or  hardened  skin.  This  body-wall  is  composed  of 
two  layers,  an  inner,  very  thin  and  soft,  cellular  layer,  the  cells 
being  arranged  side  by  side  to  form  a  skin  membrane,  only 
one  layer  of  cells  in  thickness,  and  an  outer,  thicker,  non-cellu- 
lar cuticular  layer,  composed  of  material  secreted  by  the  skin 
cells  and  perhaps  partly  of  the  hardened  outer  ends  of  these 
cells  themselves.  This  thick,  firm,  colored  cuticle  is  made  up  of 


FIG.  50. — Honey-bee,  Apis  mellifica.     (Nearly  3  times  natural  size.) 

successive  fine  laminae  well  fused  together,  and  is  composed 
chiefly  of  a  complex  sustance  called  chitin.  It  is  this  chitinized 
cuticle  which  gives  the  body-wall  of  insects  its  hardness,  and 
makes  of  it  not  only  a  firm  protecting  cover  for  the  soft  parts 
within  but  also  an  exoskeleton  to  which  the  muscles  are 
attached.  The  chitinized  cuticle,  although  extending  continu- 
ously over  the  body,  is  flexible  in  certain  places,  as  between  the 
head  and  thorax,  thorax  and  abdomen,  various  abdominal 
segments  and  at  the  articulations  of  antennae,  mouth-parts, 
legs,  wings  and  between  the  various  antennal,  mouth-part 
and  leg  joints,  etc.  This  is  necessary,  of  course,  for  the 
effective  movement  of  all  these  parts.  Such  flexible  places 
in  the  cuticle  are  called  sutures,  while  the  firmer,  fixed  parts 
are  called  sclerites. 


128    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Body -regions  and  Segments. — The  body  of  a  honey-bee,  like 
that  of  a  grasshopper,  is  made  up  of  three  readily  distinguish- 
able main  parts  or  regions,  the  head,  thorax  and  abdomen,  each 
part  bearing  its  special  appendages,  as  antennae  and  mouth- 
parts  on  the  head,  legs  and  wings  on  the  thorax,  and  the 
parts  forming  the  sting  on  the  abdomen. 

Each  of  the  main  body-regions  is  composed  of  several  body 
segments,  but  in  the  head  and  thorax  these  segments  are  so 
fused  as  to  be  hardly  distinguishable  as  separate  parts.  In  the 
abdomen,  however,  six  distinct  segments  can  be  distinguished. 

All  insects  have  the  body  fundamentally  composed  of  suc- 
cessive segments  grouped  more  or  less  compactly  into  three 
body  regions.  The  typical  number  of  segments  fused  to  form 
the  head  is  probably  six,  perhaps  only  four.  The  thorax 
is  composed  of  three,  called  prothoracic,  mesothoracic,  and 
metathoracic,  segments,  while  the  abdomen  comprises  from 
seven  to  eleven  segments,  although  in  some  insects  these  may 
be  so  fused  as  to  make  the  abdomen  seem  made  up  of  but  three 
or  four,  or  even  a  single  segment. 

Segmented  Appendages. — The  antennas  or  "feelers"  of  the 
head,  the  legs,  and  less  plainly  the  mouth-parts,  show  that 
each  of  these  movable  appendages  of  the  body  is  made  up  also 
of  a  series  of  successive  segments  or  "joints."  The  hardened 
body  wall,  the  segmentation  of  the  body,  and  the  segmentation 
or  jointing  of  the  body  appendages,  of  the  bee  and  all  other 
insects,  are  the  fundamental  characteristics  that  show  their 
relationship  to  the  crustaceans,  myriapods,  spiders  and  other 
Arthropoda. 

Mouth-parts. — The  mouth-parts  of  the  bee  are  composed  of 
a  skin  flap  called  upper  lip  or  labrum,  a  pair  of  firm,  trowel-like 
little  jaws  or  mandibles  used  chiefly  for  moulding  the  wax 
when  the  cells  are  being  built,  and  a  complex  tongue-like  organ 
composed  of  various  parts  as  shown  and  named  in  Fig.  51. 
This  "  tongue"  is  the  nectar-gathering  organ,  and  is  so  arranged 
that  its  various  parts  can  be  held  together  so  as  to  form  an 
imperfect  tube  inside  of  which  a  long  hairy  rod  moves  back  and 
forth.  The  flower-nectar  taken  up  on  the  expanded  tip  of  this 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     129 


hairy  rod  is  forced  up  the  tube  by  the  pressing  together  of  the 

parts  composing  its  walls. 
Antennae  and  Senses.  —  The  two  feelers,  or  antennae,  of  the 

bee  are  slender,  elbowed  processes,  each  composed  of  thirteen 

small  segments,  which  can  be  moved  freely,  and  extend  out  in 

front  of  the  face  so  as  to  be  in  advance  of  the  head  when  the 

bee  is  flying  or  walking.     They  are  general 

organs  of  touch  and  smell  and  probably 

also   of  hearing.     Each  of  these  senses 

has  its  own  particular  specific  organs  on 

the  antennae,  those  of  feeling  being  fine 

tactile  hairs  and  papillae,  those  of  smell 

being  variously  shaped  very  minute  pits 

or  cones,  each  with  a  fine  nerve  ending 

in  it,  while    those  of  hearing  are  more 

problematical.     But  it  has  been  proved 

that  many  insects  have  special  auditory 

organs  in  the  antennae  consisting  usually 

of  fine  hairs  which  can  be  set  into  vib- 

ration by  the  sound  waves,  and  an  elabo- 

rate receiving  arrangement,  in  the  second      F  _M      , 

segment,  of   chitin  rods,  delicate  nerve  parts  of  a   honey-bee 

fibers,  special  ganglion  cells  and  an  audi-  with  maxilla  and  man- 

tory  nerve  running  to  the  brain.    The  ££.*&  ±-£ 

male  mosquito  has  a  very  highly  deve-  ble-mx.,  maxilla;  mx.p., 

loped  auditory  apparatus  of  this  type.       maxillary  palpus;  mx.L, 
Af.  ,          ,,  i  maxillary      lobe;      st., 

A  few  insects,  such  as  the  grasshopper,  stipes  of  maxjna; 

katydids,   crickets   and   others    have    a 


cardo  of 


very  different  kind  of  "ear,"  not  situated  !abium; 
•'  turn   of 


maxilla;  II., 
w.,  submen- 
labium;    m., 
mentum  of  labium;  pg., 


,,,., 

on   the  head,  but  on  the  abdomen   (in 

the  grasshoppers),  front  legs  (in  katydids  paraglossa.  gl.,  glossa; 
and  crickets),  or  elsewhere  on  the  body.  Kp''  labia  palpus' 
This  kind  of  ear  is  composed  of  a  small,  thin  vibratory  drum 
or  tympanum,  with  an   air-space  underneath  it,  and  a  tiny 
ganglion  and  special  nerve  in  connection  with  it. 

The  sense  of  smell  is  very  highly  developed  in  most  insects. 
Indeed  it  is  probable  that  most  of  an  insect's  sensation  of  out- 
side things  comes  through  its  organs  of  smell.  And  the 


1 3o    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

minute  pits  and  cones  or  papillae  which  are  the  organs  of  smell 
and  are  stimulated  by  substances  in  gaseous  or  otherwise 
very  finely  divided  condition,  may  be  very  abundant,  several 
thousand  being  present  on  each  of  the  bee's  antennae. 


FIG.  52. — Different  kinds  of  insect  antennae,  i,  From  a  ground  beetle, 
Pteroslichus  calif ornicus;  2,  from  a  carrion  beetle,  Silpfu.  ramcsa;  3,  from  a 
click  beetle,  Melanotus  variolatns;  4,  from  a  honey-bee,  Apis  mellifica; 
5,  from  a  Scarabaeid  beetle,  Ligyrus  gibbosus;  6,  from  a  blow  fly,  Calli- 
phora  •vomitora.  (About  12  times  natural  size.) 

Eyes  and  Sight. — On  the  head,  also,  beside  the  antennae 
and  mouth-parts,  are  the  eyes.  These  are  of  two  kinds,  namely 
a  pair  of  large  compound  eyes  and  three  smaller  simple  eyes  or 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     131 


ocelli.  The  external  surface  of  the  compound  eyes  is  revealed 
by  the  microscope  to  be  divided  into  many  small  hexagonal 
facets.  Each  of  these  is  a  minute,  rigid,  flat  lens  behind  which 
exists,  arranged  as  a  slender,  rod-like  organ, 
a  perceptive  unit  of  the  compound  eye. 
These  units  are  called  ommatidia,  and  each 
one  is  composed  of  a  crystalline  part  just 
behind  the  external  lens,  surrounded  by  pig- 
ment, and  behind  this  a  sensitive  nerve  end- 
ing, called  a  rhabdome,  also  surrounded  by 
pigment.  From  the  rhabdome  a  fine  nerve 
runs  backward  to  join  with  the  similar  fine 
nerves  from  the  other  ommatidia  to  form 
the  large  optic  nerve  going  to  the  brain. 
Each  ommatidium  is  thus  a  complete  little 
eye  with  light  gathering  and  transmitting 
and  perceiving  apparatus,  but  without  means 
of  change  of  focus,  and  only  slight  means  of 
adjustment  to  varying  intensity  of  light. 

This  slight  means  of  adjustment  depends 
on  the  power  of  the  insect  to  move  the  pig- 
ment surrounding  the  ommatidia  back  and 
forth,  and  thus  to  arrange  it  in  a  way  to 
allow  more  or  less  light  to  reach  the  rhab- 
domes. 


--on 


FIG.   53.— Lon- 
gitudinal   section 
through     a     few 
Most  of  the  light  rays  that  enter  each  om-    facets  and  eye-ele- 
matidium  must  be  those  that  fall  nearly  ver-    ments    (ommati- 
..11  Ai  11  j  ^      dia)   of  the  com- 

tically  on  the  external  lens,  and  pass  verti-    poun(j  eye    of  a 

cally  in    to  the  sensitive  rhabdome.     Thus    moth.     /.,     cor- 

each  ommatidium  "sees"  only  any  object  or    neal   facets;    cc., 

.   J        J        J  crystalline  cones; 

part  of  any  object  directly  in  the  line  of  its    p.^  pigment;    r., 

long  axis,  and  as  the  surface  of  the  compound  retinal  parts;  o.n., 
eyes  of  insects  is  usually  strongly  curved,  ?^f^gr  nExner: 
separate  ommatidia  usually  see  only  separate  greatly  magnified.) 
points  in  objects  of  the  environment.  These 
points  put  together  side  by  side  form  a  mosaic  correspond- 
ing to  the  object  or  objects  in  front  and  at  the  sides  of  the 
eyes.  Such  seeing  is  called  mosaic  or  apposed  vision. 


i32    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

However,  when  the  pigment  surrounding  the  ommatidia 
is  drawn  back  from  their  anterior  ends,  light  rays  can  pass 
through  the  lateral  walls  of  the  ommatidia  from  the  lenses 
of  adjoining  ommatidia,  and  thus  the  reflected  rays  from  a 
single  point  in  an  object  may  reach  and  stimulate  several 
adjacent  rhabdomes,  forming  a  picture  in  a  somewhat  different 
way  from  that  by  the  strict  mosaic  method.  This  picture  is 
called  a  superposition  image  as  contrasted  with  the  apposition 
image  of  the  true  mosaic  vision. 

The  focal  distance  of  the  lenses  in  the  compound  eyes  is 
usually  about  two  yards,  so  that  these  eyes  see  objects  best  at 

that  distance  from  the  insect. 
The  sharpness  or  clearness  of  the 
image  formed  depends,  too,  on 
the  number  and  size  of  the  sepa- 
rate ommatidia.  The  smaller 
and  the  more  numerous  they 
are  the  more  perfect  will  be  the 
mosaic;  that  is,  the  more  complete 
and  clear  will  be  the  picture  seen. 
The  number  of  facets  in  the  com- 
pound eyes  of  insects  varies  from 
three  or  four  to  twenty  thousand 
or  more. 

The  simple  eyes,  or  ocelli,  are 
very  different  from  the  com- 
pound eyes  in  make-up.  Each  ocellus  has  but  one  lens,  but 
behind  it  is  a  varying  number  of  sensitive  or  optic  cells  each 
with  anterior  crystalline  part  and  posterior  retinal  or  percip- 
ient part.  But  the  very  short  focus  of  the  lens,  usually  but  a 
few  inches,  and  the  primitive  character  of  the  structure  of  the 
part  behind  the  lens,  limit  the  vision  probably  to  little  more 
than  a  perception  of  shadows  in  imperfect  outline.  The 
ccelli  can  only  perceive  objects  very  close  to  the  insect,  and 
then  with  but  little  clearness.  In  fact  the  vision  of  insects, 
either  by  means  of  compound  or  simple  eyes,  is  at  best  imperfect 
when  compared  with  that  of  the  vertebrate  animals.  Although 
observation  and  experiment  have  shown  that  insects  can  dis- 


FIG.  54. — Part  of  corneal 
cuticle,  showing  facets,  of  the 
compound  eye  of  a  horse-fly, 
Therioplectes  sp.  (Greatly 
magnified.) 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     133 

tinguish  colors  and  pattern  when  the  color  shades  and  the 
outlines  are  strongly  contrasted,  yet  on  the  whole  insect  eyes 
are  much  better  constructed  for  quickly  recognizing  moving 
bodies  and  passing  shadows  than  for  seeing  in  detail  either 
the  shape  or  the  color  pattern  of  objects. 

Legs. — The  appendages  of  the  bee's  thorax  are  the  legs  and 
the  wings.     The  thorax  is  composed  of  three  closely  fused  body 


FIG.  55. — Legs  of  honey-bee.  A,  Left  front  leg  of  worker,  anterior 
view,  showing  position  of  notch,  dd.,  of  antenna  cleaner  on  base  of  first 
tarsal  joint,  tar.,  and  of  closing  spine  ee,  on  end  of  tibia  tb;  B,  spine  of 
antenna  cleaner,  ee,  in  flat  view;  C,  details  of  antenna  cleaner;  D,  left 
middle  leg  of  worker,  anterior  view;  E,  left  hind  leg  of  worker,  anterior  or 
outer  view,  showing  the  pollen  basket,  cb,  on  outer  surface  of  tibia, 
tb  and  the  so-called  "wax-shears,"  ff,  F,  inner  view  of  first  tarsal 
joint  of  hind  leg  of  worker,  showing  rows  of  pollen-gathering  hairs 
on  tarsus,  tar.  (After  Snodgrass.) 

segments.  Each,  of  these  segments  bears  a  pair  of  legs,  but 
only  the  hinder  two  bear  pairs  of  wings.  The  legs  of  the  bee 
are  of  the  number  characteristic  of  insects.  However,  some 
insects  have  the  legs  wanting.  In  such  insects  as  have  adopted 
a  strictly  sedentary  life,  as  the  scale  insects,  absence  of  the 


i34    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

legs  is  the  rule  rather  than  the  exception.  The  bee's  legs  are 
well  fitted  for  walking,  but  they  are  also  modified,  the  hinder 
ones  especially,  for  the  performance  of  other  functions.  The 
fore  legs  carry  a  number  of  branched  hairs  and  curved  bristles 
for  collecting  pollen.  They  also  have  a  curious  little  combina- 
tion of  structures  called  an  antenna  cleaner  composed  of  a 
rounded  indentation  lined  with  a  row  of  short  spines  and  nearly 
closed  by  a  large  movable  spine.  The  middle  legs  have  also 
pollen-gathering  hairs  and  a  curved  spine  which  is  used  to  pry 
the  pollen  from  the  hindmost  pair  of  legs.  The  hindmost 
legs  are  most  modified  of  all.  They  have  a  so-called  "pollen 
basket,"  or  concave  outer  surface  margined  with  curved  bris- 
tles; "pollen  combs"  composed  of  transverse  rows  of  short 
strong  hairs;  and,  finally,  a  structure  called  the  "wax-pincers," 
being  the  two  opposed  edges  of  two  joints  of  the  leg,  one  lined 
with  spines,  the  other  smooth.  This  structure,  according 
to  Casteel,  has  nothing  to  do  with  cutting  wax,  but  aids  in 
the  gathering  of  pollen. 

The  separately  articulated  parts  or  joints  of  each  leg  have 
been  given  special  names.  Beginning  with  the  one  which 
articulates  with  the  body,  called  the  coxa,  the  others  are  the 
trochanter,  a  very  small  one,  the  femur,  which  is  the  largest, 
the  tibia,  which  is  next  in  size  to  the  femur,  and  finally  the 
tarsal  segments,  which,  in  the  bee,  are  five  in  number.  The  last 
or  terminal  one  bears  a  pair  of  claws  and  a  little  pad  called  the 
piilvillus,  lying  between  the  claws.  These  tarsal  segments 
vary  from  one  to  five  in  different  insects. 

The  legs  of  insects  show  great  variety  in  structure  and  use. 
Aquatic  insects  have  one  or  more  pairs  of  the  legs  modified  to 
be  swimming  organs;  subterranean  insects  have  digging  legs; 
leaping  insects  have  the  hindmost  pair  usually  very  large  and 
long.  Some  predaceous  insects  have  the  forelegs  modified 
to  be  grasping  or  lacerating  organs.  In  fact  only  those  in- 
sects which  use  their  legs  exclusively  for  walking  and  running 
have  them  in  a  condition  which  might  be  called  unmodified. 
In  such  insects  they  are  usually  long  and  slender  with  the  seg- 
ments more  or  less  cylindrical  in  shape. 

The  last  tarsal  segments  of  the  different  legs  can  be  called  the 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     135 

feet,  for  it  is  on  the  claws  and  little  pads  present  on  these  seg- 
ments that  the  insect  stands.  Insects  that  can  climb  on 
smooth  surfaces  or  walk  on  overhanging  walls  have  small 
hollow  hairs  on  the  pads  of  the  feet  from  which  a  sticky  se- 
cretion issues. 

Wings. — Bees'  wings  are  four  in  number,  which  is  the  typical 
number  for  insects  in  general.  However,  many  insects,  in- 
cluding all  the  true  flies  or  Diptera,  have  but  a  single  pair  of 
wings.  Parasitic  insects,  such  as  fleas,  lice,  etc.,  are  usually 
wingless.  All  of  the  living  wingless  insects,  except  a  single 
small  grsup  called  the  Aptera,  are  believed  to  have  lost  their 
wings  by  degeneration.  The  Aptera,  however,  are  believed 
to  be  the  immediate  descendants  of  the  primitive  wingless 
ancestors  of  the  whole  great  insect  class. 

The  bees'  wings  are  membranous,  very  thin  and  trans- 
parent, and  supported  on  a  framework  of  branching  veins. 
The  wings  of  many  insects,  however,  are  thickened,  as  for  ex- 
ample the  fore  wings  of  grasshoppers  and  all  beetles.  The  wing 
veins  may  be  few  in  number  as  with  the  bee  and  house-fly, 
or  many,  as  in  the  hind  wings  of  the  grasshoppers.  Most 
of  the  butterflies  and  moths  have  their  wings  covered  com- 
pletely above  and  below  with  fine  scales  in  which  pigment  of 
various  colors  is  held.  In  the  two-winged  flies  it  is  the  hind- 
most pair  of  wings  that  is  lost,  or  rather  is  replaced  by  a  pair 
of  very  different  structures,  small  stems  with  expanded  tips, 
called  balancers.  In  one  small  group  of  insects,  however,  it 
is  the  front  pair  of  wings  that  is  gone. 

The  two  wings  on  each  side  of  the  bee's  body  can  be  fastened 
together,  and  are,  when  the  bee  is  flying,  by  a  row  of  tiny 
hooks  along  the  front  margin  of  the  hind  wing  which  catch 
hold  of  the  hind  margin  of  the  front  wing.  This  is  a  device 
which  makes  the  bee  practically  two-winged  when  in  flight. 
Some  other  insects,  as  most  of  the  butterflies  and  moths, 
for  example,  also  have  means  for  fastening  the  two  wings  of 
each  side  together. 

Sting. — The  appendages  of  the  abdomen,  although  several 
in  number,  are  all  combined  to  form  the  sting.  This  sting 
is  made  up  of  a  sheath  containing  two  movable  barbed  darts 


136    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  a  pair  of  sting  feelers  which  probably  act  as  sense  organs. 
The  sting  is  connected  by  a  duct  with  a  poison  reservoir  which 
is  supplied  with  poison  from  a  pair  of  interior  glands. 

Wax  Plates. — On  the  under  side  of  each  of  the  last  four  seg- 
ments of  the  worker-bee  there  is  a  pair  of  wax  plates.  The  wax 
issues  as  a  fluid  from  small  glands  in  these  plates.  On  its 
issuance  it  spreads  out  over  the  surface  of  the  plates  and 
hardens.  It  can  then  be  plucked  off  in  thin  sheets  by  the  bee. 

THE  INTERNAL  STRUCTURE  OF  A  CATERPILLAR 

The  body  of  the  bee  is  too  small  to  be  dissected  easily. 
For  a  study  of  the  internal  insect  anatomy  we  may  take  a 
caterpillar;  any  kind  will  do,  although  one  with  a  naked  in- 
stead of  hairy  body  will  be  more  convenient  to  use.  Although 
caterpillars  are  immature  insects — they  are  the  young  stages 
of  butterflies  and  moths — they  will  reveal  all  the  important 
organ  systems,  except  one,  in  well-developed  condition.  The 
one  exception  is  the  reproductive  system,  which  may  be 
examined  in  a  full-grown  grasshopper. 

Adipose  Tissue.— On  opening  the  body  of  the  caterpillar 
the  first  thing  noted  is  a  mass  of  whitish  flocculent  material 
which  is  fat,  or  adipose  tissue.  It  is  formed  out  of  the  surplus 
food  eaten  by  the  voracious  caterpillar,  and  is  used  during  the 
time  which  the  insect  spends  in  the  chrysalis  stage  when  it  is 
inactive  and  cannot  feed.  This  adipose  tissue  lies  all  around 
and  over  the  various  internal  organs,  and  must  be  picked 
away  to  reveal  them. 

Alimentary  Canal. — The  most  conspicuous  organ  visible, 
after  the  fat  is  removed,  is  the  long  straight  alimentary  canal 
running  from  mouth  to  anus  through  the  middle  of  the  body. 
It  is  composed  of  successive  parts,  named,  beginning  at  the 
mouth,  esophagus,  ventriculus  or  stomach,  small  intestine, 
large  intestine  and  rectum.  Where  the  ventriculus  and 
small  intestine  join,  a  few  delicate,  whitish,  thread-like  con- 
voluted tubules  arise  known  as  the  Malpighian  tubules.  These 
correspond  in  function  to  the  kidneys  of  other  animals,  taking 
up  and  excreting  waste  from  the  blood. 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     137 


i38    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

If  the  caterpillar  is  of  a  kind  that  spins  a  coccoon  when  it  is 
ready  to  change  into  a  chrysalis,  the  silk  glands  will  be  found  as 
a  pair  of  long,  smooth,  rather  thick,  whitish  cords  lying  one 
on  each  side  of  the  alimentary  canal  and  running  forward  to 
the  mouth.  Another  pair  of  smaller,  shorter  tubes,  not  ex- 
tending farther  back  than  about  the  beginning  of  the  ventri- 
culus  are  the  salivary  glands.  The  silk  glands  are,  indeed, 
only  an  enlarged  and  modified  second  pair  of  salivary 
glands. 

Respiratory  System. — In  taking  out  the  adipose  tissue  and 
alimentary  canal  there  will  be  noted  many  dark  little  thread- 
like processes  which  are  in  reality  fine  tubes,  called  trachea. 
By  tracing  them  to  their  origin  they  will  be  found  to  arise 
from  larger  tracheae,  which  in  turn  are  given  off  from  main 
longitudinal  trunks.  There  are  two  or  four  of  these  trunks, 
one  or  two  on  each  side  of  the  body,  and  from  them  arise 
not  only  the  branches  that  by  repeated  subdividing  extend 
to  all  parts  of  the  body,  but  short  strong  lateral  trunks 
that  run  to  small  openings  called  spiracles,  or  stigmata,  in  the 
sides  of  the  body.  In  most  caterpillars  nine  pairs  of  spiracles 
will  be  found,  one  pair  on  the  prothoracic  segment  and  the 
others  on  the  abdominal  segments,  one  pair  to  each.  The 
spiracles  and  tracheae  are  the  organs  of  the  respiratory  system  of 
the  caterpillar,  and  similar  organs,  although  varying  much  in 
number  and  arrangement,  will  be  found  in  all  insects,  except 
a  few  very  small  and  thin-skinned  ones,  which  respire  directly 
through  the  skin.  The  spiracles  show  on  the  outside  of  the 
body  as  small  blackish  spots,  but  are  actually  small  openings 
in  the  body-wall,  provided  usually  with  valves  or  fringes  of 
hairs  to  keep  out  foreign  particles.  They  allow  air  to  pass  into 
the  interior  system  of  tracheae,  and  carbon  dioxide  to  pass  out. 
The  tracheae,  although  thin-walled  and  delicate,  especially 
the  finer  ones,  are  lined  with  a  thin  chitinous  membrane  in 
which  are  spiral  thickenings  which  hold  them  open  and  give 
them  a  certain  necessary  elasticity.  When  the  insect  contracts 
certain  muscles  lying  as  longitudinal  and  circular  bands  along 
the  inner  side  of  the  body-wall,  the  pressure  of  the  body  con- 
tents forces  the  tracheae  to  close  and  expels  the  gas  in  them  out 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     139 

through  the  spiracles.  When  the  muscles  are  relaxed  and  the 
pressure  is  removed  the  elastic- walled  tracheae  open  again  and 
are  filled  with  fresh  air  which  rushes  in  through  the  open 
spiracles.  One  can  readily  see  this  alternate  contraction  and 
expansion,  or  respiratory  movement,  of  the  body  in  a  live 
grasshopper. 

The  respiratory  system  of  insects  is,  as  we  have  learned  from 
its  condition  in  the  caterpillar,  very  different  from  that  of  the 
vertebrate  animals.  There  is  no  breathing  through  nostrils  or 
mouth  on  the  head;  there  are  no  lungs;  there  is  no  taking  up 
and  carrying  of  oxygen  by  the  blood.  The  air  that  enters  an 
insect's  body  through  the  spiracles  is  carried  to  every  smallest 
part  of  it  by  the  tracheal  tubes.  Similarly  these  tubes  take 
up  from  the  tissues  and  cells  of  the  body  waste  carbon  dioxide 
and  carry  it  outside  the  body.  The  blood  has  nothing  to  do 
with  respiration  in  insects.  It  only  gets  what  air  it  needs  for 
itself. 

Circulatory  System. — The  blood  of  insects  is  better  called 
blood  lymph  because  it  is  always  a  mixture  of  blood  and 
lymph.  There  is  no  elaborate  system  of  arteries  and  veins, 
but  only  a  single  main  longitudinal  vessel  which  lies  just  under 
the  body-wall  of  the  middle  of  the  back,  and  is  sometimes  called 
heart,  but  more  often,  simply,  dorsal  vessel.  To  see  this  organ 
in  a  caterpillar  it  is  necessary  to  cut  one  open  longitudinally 
along  the  middle  of  the  underside  and  to  take  out  carefully 
all  the  fat  tissue  and  the  alimentary  canal.  Then  there  may 
be  seen  running  along  the  inner  surface  of  the  body-wall  of 
the  back  a  delicate  membranous  flattened  tube  which^  is 
composed  of  a  number  of  successive  chambers  separated  from 
each  other  by  delicate  valves  and  provided  also  with  small 
lateral  openings  also  furnished  with  valves.  In  the  thin  walls 
there  are  delicate  muscle  fibers,  so  that  the  vessel  can  contract 
and  expand  as  these  muscles  are  contracted  and  relaxed. 
This  pulsation,  combined  with  the  arrangement  of  the  valves, 
allows  the  blood  lymph,  which  everywhere  else  in  the  body  is 
not  confined  but  flows  freely  among  the  body  organs,  to  enter 
the  dorsal  vessel  through  the  lateral  openings  and  be  forced 


140    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


forward  from  one  chamber  to  another  until  it  issues  from  a 
narrow  anterior  extension  of  the  vessel,  called  the  aorta. 

In  many  insects  the  dorsal  vessel  is  not  so  long  and  slender  as 
in  the  caterpillar,  nor  composed  of  as  many  chambers.  But  in 
all  insects  the  circulatory  system  comprises  nothing  more  than 
a  pulsating  dorsal  vessel  and  the  blood  lymph  flowing  freely 
everywhere  in  the  body  cavity. 

Nervous  System. — Extending  along  the 
middle  of  the  floor  of  the  caterpillar's  body 
will  be  seen  a  delicate  white  thread  with 
small  expansions  or  knots  in  it  arranged 
segmentally,  but  wanting  in  the  last  two 
abdominal  segments.  In  the  head  there 


FIG.  57.  FIG.  58. 

FIG.  57. — Diagram  of  circulatory  system  of  a  young  dragon-fly;  in 
middle  is  the  chambered  dorsal  vessel,  or  heart,  with  single  artery.  Arrows 
indicate  direction  of  blood-currents.  (After  Kolbe.) 

FIG.  58. — Diagram  of  ventral  nerve-cord  of  locust,  Dissosteira  Carolina. 
(After  Snodgrass.) 

is  a  knot  underneath  the  esophagus  and  from  it  a  pair  of 
stout  threads  which  run  up  and  around  the  esophagus, 
one  on  each  side,  and  into  a  larger  knot  lying  on  top  of  the 
esophagus. 

These  knots  and  thread  compose  the  main  part  of  the  central 
nervous  system  of  the  caterpillar,  the  threads  being  the  nerve- 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     141 

cords  or  connections,  and  the  knots,  the  ganglia,  or  nerve  cen- 
ters. The  ganglion  in  the  head  above  the  esophagus  is  called 
the  brain,  and  from  it  nerves  run  to  the  eyes  and  antennae. 
From  the  head  ganglion  under  the  esophagus  nerves  run  to  the 
mouth-parts.  From  the  ganglia  in  the  thoracic  segments 
nerves  run  to  the  legs  and  to  the  strong  thoracic  muscles  that 
move  the  legs.  In  insects  with  wings,  nerves  run  from  these 
.ganglia  also  to  the  wing  muscles.  From  the  ganglia  in  the 
abdomen  nerves  run  to  the  various  body  organs  such  as  ali- 
mentary canal,  dorsal  vessel,  tracheae,  muscles,  etc.  Thus 
although  the  head  ganglia  of  an  insect  may  be  looked  on  as 
the  most  important  nerve  centers  of  the  body,  and  one  is 
called  the  brain,  by  analogy  with  the  brain  of  vertebrate 
animals,  yet  really  each  ganglion  is  a  little  brain  for  its  own 
part  of  the  body,  and  there  is  a  good  deal  more  independence 
about  the  control  of  the  different  parts  of  the  insect's  body  than 
there  is  in  the  vertebrate's  body. 

Although  the  ganglia  and  connecting  longitudinal  cord,  or 
commissure,  seem  to  be  single  knots  and  a  single  thread,  they 
are  in  reality  all  double,  each  ganglion  consisting  of  a  pair 
fused  together  on  their  inner  faces,  and  the  connective  com- 
missure also  is  composed  of  two  cords  lying  so  close  together 
as  to  seem  but  one. 

In  most  insects  there  are  not  as  many  ganglia  as  we  find  in 
the  caterpillars,  the  reduction  in  number  being  brought  about 
not  so  much  by  the  loss  as  by  the  fusion  of  ganglia.  The 
typical  six  or  seven  abdominal  ganglia  may  be  fused  to  form 
but  two  or  three  or  even  one,  and  the  three  thoracic  ganglia 
are  also  often  fused  to  form  a  single  one.  In  certain  highly 
specialized  insects,  indeed,  all  the  abdominal  and  thoracic 
ganglia  join  to  form  one  large  thoracic  nerve  center,  or  "body 
brain,"  as  it  has  been  called.  Only  in  young  insects  and  in 
adults  belonging  to  generalized  or  primitive  species,  are  there 
separate  ganglia  for  most  of  the  segments  of  the  body. 

Besides  the  central  nervous  system,  most  insects  have  also  a 
sympathetic  nervous  system,  which  usually  consists  of  a  very 
small  ganglion  just  in  front  of  the  brain,  and  one  or  two  small 


i4 2    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

ganglia  lying  on  the  sides  of  the  alimentary  canal,  all  these 
ganglia  being  connected  by  fine  nerve-cords. 

Musculature. — Lying  next  to  the  skin  of  the  caterpillar's 
body  can  be  seen  many  muscles,  some  of  them  extending 
longitudinally  and  others  as  transverse  or  circular  bands.  Also 
in  the  head  and  thorax  are  many  other  muscles  for  moving  the 
mouth-parts  and  legs.  Most  insect  muscles  are  small  and 
short,  so  that  for  the  complete  musculation  of  the  body  a  great 
many  separate  muscles  are  required.  Several  thousand  have 
been  counted  in  the  body  of  a  single  insect. 

The  muscles  which  lie  against  the  inside  of  the  body-wall  in 
the  caterpillar  are  repeated  almost  ^identically  for  each  seg- 
ment. This  musculation  then  can  be  said  to  be  segmental  in 
character  just  as  we  have  found  that  the  respiratory  system, 
nervous  system  and  even  the  dorsal  vessel  can  be  said  to  be 
segmentally  arranged.  That  is,  the  internal  systems  of  organs 
of  the  insect  show  as  plainly,  almost,  as  the  external  surface  of 
the  body,  the  fundamental  segmental  make-up.  And  they 
also  show,  just  as  the  outside  of  the  body  does,  the  bilateral 
symmetry  of  the  body.  If  the  insect's  body  be  cut  longi- 
tudinally by  a  vertical  plane  it  will  be  divided  into  equal  halves, 
both  external  and  internal  organs  either  being  in  pairs,  one 
member  on  each  side  of  this  vertical  plane,  or  being  made  of 
fused  pairs  lying  in  this  vertical  plane. 

Reproductive  System. — As  the  caterpillar  is  only  an  im- 
mature moth  or  butterfly  its  reproductive  system  is  not  fully 
developed.  Any  adult  insect  of  good  size  and  not  too  hard  wall 
may  be  used  to  study  the  organs  of  reproduction.  A  grass- 
hopper will  do  very  well. 

In  the  female  the  eggs  are  produced  in  many  small  tubules, 
called  ovarioles,  which  are  grouped  to  form  two  ovaries  (right 
and  left)  from  each  of  which  runs  an  oviduct.  The  two  oviducts 
unite  to  form  a  single  wider  short  tube  called  the  vagina. 
From  this  the  eggs  pass  out  of  the  body  in  little  packets.  The 
eggs  are  fertilized  while  still  in  the  body  of  the  female  by 
spermatozoa  that  have  been  received  from  the  male  and  held 
in  a  small  sac  called  the  spermatheca.  Each  egg  is  inclosed  in 
an  inner,  thin  vitelline  membrane  and  an  outer  thicker  firmer 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     143 


shell  or  chorion.  But  a  small  hole,  called  micropyle,  is  left 
at  one  pole  in  both  these  coverings,  and  through  this  a  sper- 
matozoan  enters  the  egg  while  it  is  in  the  vagina,  or  a  special 
posterior  part  of  it  called  the  bursa  copulatrix. 

The  organs  of  the  male  that  produce  the  spermatozoa  are 
called  testes,  and  correspond  in  position  and  function  to  the 
ovaries  of  the  female.  They  are  also  composed  of  many 
tubules,  but  they  are  closely  pressed  together  to  form  a  small 
solid  ovate  mass.  From  each  testis 
runs  a  duct,  the  lias  deferens, 
through  which  the  spermatozoa 
pass  to  reach  the  single  ejaculatory 
duct,  from  which  they  are  expelled 
by  the  male  at  mating. 

TYPES  OF  MOUTH-PARTS 

Corresponding  to  the  great  vari- 
ety of  food  taken  by  insects  is  a 
great  variety  in  structure  of  mouth- 
parts.  The  mouth-parts  of  the 
honey-bee,  which  laps  up  flower 
nectar,  are  very  different  from 
those  of  the  grasshopper,  which 
bites  off  and  chews  green  leaves.  FIG.  59. — Honey-bee,  Apis 
And  very  different  from  either  of  mdlifica,  reproductive  organs, 
,,  .  ,,  ,,  sting  and  poison  glands  of 

these,  again,  are   the   mouth-parts  que*n)  dors£  view  6  (Greatiy 

of    a    butterfly    or    moth,    or    of    a   magnified;  after  Snodgrass.) 
mosquito,  or  a  squash-bug. 

To  the  economic  entomologist  a  knowledge  of  the  kind  of 
mouth-parts  possessed  by  any  insect  pest  is  very  important. 
For  on  the  structure  of  its  mouth  will  depend  largely  the  kind 
of  artificial  remedy  which  must  be  devised  to  kill  it.  For  ex- 
ample, if  an  insect  pest  of  fruit  trees  has  a  piercing  and  sucking 
mouth,  then  spraying  the  surfaces  of  leaves  with  an  arsenical 
poison  will  do  little  good,  for  it  gets  its  food,  plant  sap,  from 
the  interior  of  the  leaf  or  stem.  But  if  it  has  a  biting  and  chew- 
ing mouth  then  such  a  poison  sprayed  over  the  leaves  may  be 


i44    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

very  effective.  For  with  each  bite  of  leaf  the  insect  will 
get  a  little  dose  of  poison,  and  a  few  such  doses  will  kill  it. 
Students  of  economic  entomology  should  therefore  pay  special 
attention  to  insect  mouth-parts.  The  following  brief  descrip- 
tion of  several  different  types  of  mouth  parts  may  serve  as  an 
introduction  to  this  study. 

Mouth -parts  of  Grasshoppers. — A  familiar  type  of  the  biting 
insect     mouth     is     that     of     the    grasshopper.      Here   the 


FIG.  60. — Mouth-parts  of  grasshopper,  a,  Labrum;  b,  tongue;  c, 
mandibles;  d,  maxillas;  e,  labium;  m.x  p.,  maxillary  palpi;  I. p.,  labial 
palpus.  (Greatly  magnified.) 

upper  lip  or  labrum,  inclosing  the  mouth  above  is  broad  and 
flap-like,  and  the  jaws,  or  mandibles,  which  like  the  honey- 
bee's, open  and  shut  laterally,  are  large,  strong,  heavily 
chitinized  and  have  their  biting  edges  furnished  with  small 
tooth-like  projections.  The  maxilla,  sometimes  called  second 
pair  of  jaws,  which,  with  the  mandibles,  close  the  mouth  at 
the  sides,  are  each  composed  of  several  parts,  movable  on 
each  other,  of  which  one  is  a  small  feeler,  or  maxillary  palpus, 
bearing  at  its  tip  many  taste  buds.  The  under  lip,  or  labium, 
is  a  broad  flap-like  piece  also  made  up  of  several  articulating 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     145 


parts  of  which  two  are  feelers,  or  labial  palpi,  much  like  the 
maxillary  palpi  and  also  provided  with  taste  buds  at  their 
tips.  With  the  strong,  hard-toothed  jaws  the  grasshopper 
can  bite  off  and  crush  not  alone  bits  of  soft  green  leaves  but  bits 
of  plant  stalks  and  even  woody  stems.  The  biting  type  of 
mouth-parts  like  the  grasshopper's,  although  with  many  slight 
differences  in  the  make-up  of  the  various  parts,  is  possessed 
by  the  cockroaches,  crickets  and  katydids  which  belong  to  the 
same  insect  order  as  the  grasshoppers,  and  also  by  the  beetles, 
the  dragon-flies,  the  white  ants,  and  various  other  less  familiar 
insects.  All  such  insects  bite  off  and  chew  more  or  less  solid 
substances. 

Mouth -parts     of    Cicadas,    Squash-bugs,    etc. —  Cicadas, 
squash-bugs,  bedbugs,  and  many  other  sap-sucking  and  blood- 


FIG.  61. — Head  and  prothorax  of  water-bug,  Serphus  dilatatus.  Show- 
ing the  piercing  beak  and  the  first  pair  of  legs  which  are  fitted  for  grasping. 
(About  natural  size.) 

sucking  insects  that  belong  in  the  same  order  with  them 
have  a  slender,  sharp-pointed,  more  or  less  firm  piercing  beak 
which  is  composed  of  a  tubular  sheath  inside  of  which  are 
four  sharp  needle-like  pieces  which  can  project  out  of  the 
end  of  the  sheath  and  be  worked  back  and  forth  so  as  to 
lacerate  plant  or  animal  tissue  and  thus  cause  a  flow  of  sap  or 
blood  which  is  sucked  up  the  sheath  into  the  mouth.  The 


146    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


four  piercing  stylets  are  the  greatly  modified  mandibles  and 
maxillae,  and  the  tubular  sheath,  which  has  a  narrow  longi- 
tudinal slit  along  its  upper  side,  is  the  much  modified  labium. 
The  labrum  is  reduced  to  a  very  small  triangular  piece  at  the 
base  of  the  sheath,  and  the  maxillary  palpi  are  wanting. 
The  labial  palpi  are  also  wanting,  or  are  sometimes  present 
as  two  small  feelers  rising  from  the  base  of  the  labial  sheath. 

Insects  with  this  type  of  mouth- 
parts  have  muscles  running  from 
the  top  of  the  pharynx  or  throat 
cavity  to  the  top  of  the  head 
which,  when  contracted,  expand 
the  pharynx  and  make  a  pump- 
ing or  sucking  organ  of  it. 

Mouth-parts  of  Mosquito. — 
The  piercing  and  sucking  beak 
of  the  mosquito  is  made  up  in 
much  the  same  way  as  that  of 
the  squash  bug  and  cicada. 
That  is,  there  is  a  tubular 
sheath,  narrowly  open  from 
base  to  tip  along  the  middle 
of  its  upper  side,  in  which  lie 
a  number  of  sharp,  slender 
stylets,  which  can  project  be- 
yond the  edge  of  the  sheath 
and  pierce  or  lacerate  plant 
tissue  or  the  skin  of  animals. 

The  sheath  is  the  much  modified  under  lip  or  labium,  while 
the  needles  are  the  modified  mandibles  and  maxillae  and 
two  additional  ones  called  labrum-epipharynx  and  hypopharynx. 
That  is,  they  are  outgrowths  from  the  upper  and  lower  walls  of 
the  mouth  or  throat  (pharynx).  Thus  the  mosquito  has  six 
piercing  needles  held  together  in  its  beak,  instead  of  four  as 
with  the  cicada  and  squash-bug  and  their  allies.  Or  rather 
this  is  true  only  of  the  female  mosquito,  for  the  male  mosquito 
lacks  two  of  the  stylets,  probably  the  mandibles,  and  never,  or 
but  rarely,  pierces  the  skin  of  animals  to  suck  blood.  There  is 


FIG.  62. — Mouth-parts  of  a 
female  mosquito,  Culex  sp.  lep., 
Labrum-epipharynx;  md.,  man- 
dible; mx.L,  maxillary  lobe; 
mx.p.,  maxillary  palpus;  hyp., 
hypopharynx;  li.,  labium;  gl., 
glossa;  pg.,  paraglossa. 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     147 

also  a  pair  of  maxillary  palpi,  as  long  as  the  beak  in  both  males 
and  females  of  some  mosquitoes,  but  shorter  in  the  females  of 
most  species. 

Mouth-parts  of  House-fly. — The  mosquitoes  belong  to  the 
order  of  two-winged  flies,  but  their  mouth-parts  cannot  be 
taken  as  typical  of  the  order.  A  house-fly,  for  example, 
has  a  mouth  very  different  in  make-up.  The  labium  is  a 
fleshy  proboscis  expanded  at  the  tip  to  form  a  special  lapping 
and  rasping  organ,  and  there  are  no  mandibles  or  maxillae, 
at  least  in  functional  condition.  There  is  one  pair  of  short 


FIG.  63. — Mouth-parts  of  the  house-fly,  Musca  domestica.     lb.,  Labrum; 
mx.  p.,  maxillary  palpi;  li.,  labium;  la.,  labellum. 

palpi  which  are  usually  called  the  maxillary  palpi,  although 
they  may  really  belong  to  the  labium.  The  house-fly  takes 
up  food  either  by  lapping  liquids  with  the  broad  tongue-like 
end  of  its  proboscis,  or  by  rasping  off  bits  of  solid  food,  pouring 
out  saliva  over  them  and  then  lapping  them  up  as  a  fluid 
mixture.  The  end  of  the  proBoscis,which  is  called  the  labellum, 
is  very  elaborately  contrived  and  furnished  with  ridges  for 
rasping  and  special  muscles  for  folding  and  unfolding. 

Mouth-parts  of  Butterflies  and  Moths. — The  sucking  tube 
of  the  butterfly  or  moth  is  still  another  very  different  type  of 
mouth.  There  is  no  labrum,  mandibles  nor  labium,  or  only 
rudiments  of  them.  But  the  maxillae  are  developed  into  a 
pair  of  long,  slender,  coiling  pieces  or  processes  which  can  be 
held  together  in  such  a  way  as  to  form  by  means  of  their 
grooved  inner  faces  a  perfect  tube,  long,  slender  and  flexible. 
With  this  tube  they  suck  out  nectar  from  the  nectaries 


148    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


of  flowers  or  drink  water  from  little 
pools  or  damp  places.  They  take  no 
other  food.  There  is  a  pair  of  tufted 
maxillary  palpi  which  rise  from  each 
side  of  the  base  of  the  sucking  tube 
and  between  which  the  tube,  when  not 
in  use,  is  compactly  coiled. 

Some    moths    and    butterflies    have 
their    mouth-parts    wholly    atrophied 
and  take  no  food  in  their  adult  condi- 
tion.    This    is  true    also  of  numerous 
insects   of  various   kinds.     Such  kinds 
of  insects  usually  live  but  a  short  time 
in  adult  condition,  and  use  up  during 
this  short   time   the  fat   stored  in  the 
body  during    the  immature  life.     The 
moths    and    butterflies,    for    example, 
are  extremely  voracious  feeders  in  their 
young   or  caterpillar  stages.     At  this 
time,  too,  they  have  mouth-parts  of 
very  different  type  from 
those  possessed  in  adult 
life.     A  caterpillar's 
mouth-parts  are  of  bit- 
ing   type    with    strong 
cutting     and     crushing 
mandibles  and  the  food 
is   the   tissues  of  plant 
leaves  and  stems.    Thus 
it  is  important   in   the 
study  of  insect  mouth- 
parts  to  recognize  that 
they  may  be  very  differ- 

FIG.  64.-SphinX  moth,  showing  pro-  Cnt  .in  the  Same  insect 
boscis.  At  left  the  proboscis  is  shown  at  different  times  of  its 
coiled  up  on  the  underside  of  the  head,  the  life,  and  that,  therefore, 
normal  position  when  not  in  use.  (Large  <.!,••• 
figure  natural  size;  small  figure  twice  natu-  the  mjunes  caused  by 
ral  size.)  an  insect,  and  the  rem- 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     149 

edies  for  these  injuries,  may  be  very  different  in  different 
stages  of  the  insect's  life. 


DEVELOPMENT  AND  METAMORPHOSIS 

Although  moths  and  butterflies  are  hatched  from  the  egg  in 
a  condition  extraordinarily  different  in  appearance  from  that 
which  they  finally  assume,  not  all  insects  undergo  so  great  a 
metamorphosis  during  their  development.  For  example,  a 
just-hatched  grasshopper  is  unmistakably  grasshopper-like  in 


FIG.  65. — Metamorphosis,  incomplete,  of  an  assassin-bug  (family 
RedumidcB,  order  Hemiptera).  A,  Young  just  hatching  from  eggs;  B, 
young  after  first  molting,  snowing  beginning  wing-pads;  C,  older  stage 
with  larger  wing-pads;  D,  adult  with  fully  developed  wings.  (|  larger 
than  natural  size.) 

appearance,  although  it  has  no  wings  and  the  proportions  of 
the  different  parts  of  its  body  are  somewhat  different  from  those 
of  its  parents.  The  young  grasshopper  has  three  pairs  of  legs, 
has  a  head  with  antennae,  compound  eyes  and  biting  mouth- 
parts  like  those  of  its  parent,  walks  and  hops  about,  feeding 
on  green  plants,  and  altogether  looking  and  acting  much  as 
fully  developed  grasshoppers  do,  except  that  it  has  no  wings 
and  hence  cannot  fly.  As  it  grows,  however,  wings  begin  to 
appear  as  tiny  bud-like  expansions  on  the  back  of  the  two 


1 50    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

hinder  thoracic  segments.  These  wing-buds  rapidly  increase 
in  length,  and  by  the  time  the  developing  grasshopper  has  come 
to  its  adult  size  the  wings  are  also  full  size  and  ready  for  use. 

During  this  growth  and  development  of  the  young  grasshop- 
per, which  requires  several  weeks  for  its  completion,  it  molts 
several  times.  This  molting  is  the  shedding  of  the  chitinized 
cuticle  which  covers  the  body.  Before  each  molting  takes 
place,  however,  the  skin  cells  have  secreted  a  soft  and  colorless 
new  chitinized  cuticle  which,  as  soon  as  the  outer  old  one  is  cast 
off,  becomes  firm  and  colored,  and  takes  its  place.  The  young 
grasshopper  shows  most  of  its  changes  in  size  and  appearance 
just  after  each  molting.  The  wing-buds  hardly  seem  to  grow 
between  molting  periods,  but  after  each  molting  they  may  be 
seen  to  be  larger  and  more  developed. 

Insects  whose  development  is,  in  general,  like  that  of  the 
grasshopper,  that  is,  those  which  hatch  from  the  egg  in  a 
condition  more  or  less  resembling  the  parent  except  for  size 
and  total  absence  of  wings,  are  said  to  undergo  a  development 
without  metamorphosis  or  with  incomplete  metamorphosis. 
While  insects  which,  like  the  moths  and  butterflies,  hatch  from 
the  egg  in  a  stage  very  different  in  appearance  from  that  of  the 
parent,  and  in  their  development  have  to  undergo  extraordi- 
nary changes  in  appearance  and  structural  make-up  to  become 
like  the  parent,  are  said  to  develop  with  metamorphosis,  or 
with  complete  metamorphosis. 

In  insects  with  complete  metamorphosis  there  is  a  curious 
stage  called  the  pupal  or  chrysalid  stage  which  is  interpolated 
between  the  first  or  larval  stage,  which  is  that  in  which  the 
insect  hatches,  and  the  final  or  adult  stage,  the  stage  in  which 
the  insect  is  sometimes  called  an  imago.  After  the  young 
caterpillar  has  undergone  a  certain  period  of  rapid  growth  and 
increase  of  size,  during  which  period  it  molts  several  times 
but  does  not  show  any  external  changes  making  it  any  more 
like  its  parent  than  it  was  at  the  beginning,  it  stops  feeding 
and  changes  into  an  inactive,  non-feeding  stage  with  its  body 
inclosed  in  a  thick,  firm,  chitinized  covering  which  is  neither  of 
the  shape  of  the  larva  nor  of  the  imago.  This  is  the  so-called 
pupal  stage,  and  the  insect  in  this  condition  is  called  a  pupa. 


SLIME  SLUGS,  MYRIAPODS  AND  INSECTS     151 

It  is  in  this  stage  that  most  of  the  radical  changes  in  structure 
are  undergone  which  are  necessary  to  make  the  moth  or 
butterfly  out  of  the  caterpillar,  the  house-fly  out  of  the  maggot, 
or  the  beetle  out  of  the  grub. 

However,  most  of  these  changes  have  their  beginnings  during 
the  larval  stage.  For  example,  little  wing  buds  have  been 
developing  all  through  the  larval  life,  but  they  have  remained 
very  small  and  invisible  underneath  the  chitinized  cuticle  of  the 
larva.  Especially  in  the  last  few  days  of  the  larval  stage  are  the 
various  changes  going  on  rapidly.  But  they  are  so  radical  in 


FIG.  66. — Metamorphosis,  complete,  of  Monarch  butterfly,  Anosia 
plexippus.  a,  Egg  (greatly  magnified) ;  b,  caterpillar  or  larva;  c,  chrys- 
alid  or  pupa;  d,  adult  or  imago.  (|  natural  size;  after  Jordan  and 
Kellogg.) 

character  that  it  is  impossible  for  the  insect  to  maintain  an 
active  food-getting  life  and  make  the  changes  at  the  same  time. 
Hence  comes  the  necessity  for  the  quiescent  pupal  stage  in 
which  the  insect,  living  on  food  stored  up  as  fat  by  the  larva, 
and  safely  inclosed  in  a  hard  protecting  shell,  can  make  the 
great  changes  necessary  to  its  becoming  a  fully  developed 
winged  imago,  different  as  to  mouth-parts,  eyes  and  antennae, 
different  as  to  body  shape,  different  as  to  legs  and  abdominal 
appendages,  and,  together  with  all  these  structural  differences, 
radically  different  as  to  habits  and  behavior.  Many  of  the 


152    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

internal  systems  of  organs  undergo  as  radical  changes  as  the 
external  parts.  Muscles,  salivary  glands,  parts  of  the  alimen- 
tary canal,  etc.,  of  the  larva  break  down  and  are  used  as  food  by 
new  growth  centers  which  develop  into  new  muscles,  new 
salivary  glands  and  other  new  internal  parts.  This  internal 
degeneration  of  larval  parts  and  rebuilding  of  imaginal  parts  are 
called  histolysis  and  histogenesis,  and  form  a  fascinating  subject 
of  study,  which  requires,  however,  a  training  in  histologic 
methods  of  technique  beyond  that  of  the  elementary  student. 
In  the  next  chapter,  which  is  devoted  to  the  classification  of 
insects,  we  shall  point  out  the  character  of  the  metamorphosis 
and  some  of  the  special  features  of  development  presented  by 
each  of  the  different  insect  orders. 


CHAPTER  XVII 

THE   CLASSIFICATION  OF  INSECTS,   AND    INSECT 
BENEFITS  AND  INJURIES 

Linnaeus,  the  first  great  classifier  of  animals,  divided  the 
insects  into  seven  orders  based  on  the  character  of  the  wings. 
In  the  order  Aptera,  or  wingless  insects,  he  placed  all  insects 
lacking  wings.  But  now  we  know  that  there  are  wingless 
moths,  wingless  beetles,  wingless  flies,  and  so  on,  and  that 
these  different  kinds  of  insects  ought  not  to  be  classified  to- 
gether simply  because  through  degeneration  from  one  cause 
or  another  they  have  lost  their  wings. 

The  two-winged  insects  with  balancers  in  place  of  the  hind 
wings  Linnaeus  called  Diptera,  and  this  order  still  stands  about 
as  he  established  it.  All  the  four-winged  insects  with  mem- 
branous wings  he  placed  in  two  orders,  those  having  stings  in 
the  Hymenoptera  and  those  without  stings  in  the  Neuroptera. 
Insects  with  their  wings  covered  with  scales  he  called  Lepi- 
doptera,  and  insects  with  their  fore  wings  thickened  he  called 
Coleoptera  if  the  wings  were  thickened  for  their  whole  length, 
and  Hemiptera  if  their  wings  were  thickened  only  over  the 
basal  half. 

Although  now  different  criteria  are  used  as  a  basis  for  insect 
classification  and  the  class  Insecta  is  divided  into  more  than 
seven  orders,  Linnaeus's  seven  ordinal  names  are  still  used,  and 
the  insects  indicated  by  each  of  them  are  largely  also  charac- 
terized by  the  condition  of  wings  indicated  by  the  names.  But 
out  of  the  Linnaean  orders  Aptera  and  Neuroptera,  nine  dif- 
ferent new  orders,  beside  the  two  still  bearing  the  same 
names,  have  been  made.  And  three  other  new  orders  have 
been  made  for  insects  taken  from  the  Hemiptera  and  the 
Coleoptera.  In  all  we  now  recognize  nineteen  orders  in  the 
class  Insecta.  This,  at  least,  is  the  American  practice.  Most 


154    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

English  and  Continental  entomologists  do  not  recognize  so 
many  different  orders. 

The  two  principal  criteria  used  in  the  modern  classification 
of  insects  are  the  structure  of  the  mouth-parts  and  the  char- 
acter of  the  development.  Of  these,  the  development  condi- 
tion is  held  to  be  the  more  fundamental,  although  this  may  be 
open  to  question.  However,  on  a  primary  basis  of  develop- 
ment and  mouth-part  conditions,  combined  with  character 
of  wings,  antennas,  and  to  a  less  extent,  of  legs  and  abdominal 
appendages,  insects  are  now  classified  into  orders  in  the 
following  way: 

Metamorphosis  very  slight;  biting  mouth-parts; 

wingless APTERA 

Metamorphosis  incomplete. 

With  biting  mouth-parts. 

EPHEMERIDA 


Wings  membranous. 


PLECOPTERA 
ODONATA 


ISOPTERA 
CORRODENTIA 

Fore  wings  parchment-like /   ORTHOPTERA 

I     EUPLEXOPTERA 

Wingless MALLOPHAGA 

With  sucking  mouth-parts /   HEMIPTERA 

I  THYSANOPTERA 
Metamorphosis  complete. 

With  biting  mouth-parts.  f  NEUROPTERA 

With  wings  membranous I  M*COPTERA 

I  TRICHOPTERA 

With  fore  wings  thickened COLEOPTERA 

With  sucking  mouth-parts LEPIDOPTERA 

With  lapping  or  piercing  and  sucking  mouth-  j    ^IPTERA 


parts.  SlPHONAPTERA 

'  I    HYMENOPTERA 

Order  Aptera. — The  Aptera  undoubtedly  include  the  most 
primitive  of  living  insects.  This  primitiveness  is  shown  not 
alone  by  the  absence  of  wings,  which  is  the  characteristic  which 
gives  the  order  its  name,  but  is  manifest  also  in  the  very 
simple  and  generalized  condition  of  most  of  the  body  parts, 
internal  as  well  as  external. 

All  the  insects  of  the  order  are  small,  but  a  group  of  them 


THE  CLASSIFICATION  OF  INSECTS 


known  as  the  spring-tails,  or  Collembola,  are  very  small  indeed, 
most  of  them  measuring  only  two  or  three  millimeters  in  length. 
These  Collembola  are  more  specialized  in  structure  than  the 
other  Aptera,  and  represent  a  side  line  of  evolutionary  de- 
velopment within  the  order.  Most  of  them  possess  a  curious 
forked  spring  on  the  under  side  of  the  body  by  means  of 
which  they  leap  vigorougly  when  disturbed.  But  few  of 
these  minute  insects  are  injurious,  although  at  least  one  spe- 
cies, called  the  garden-flea,  Smynthurus  hortensis,  is  sometimes 
found  in  considerable  numbers 
upon  the  leaves  of  young  cab- 
bages, turnips,  cucumbers  and 
various  other  plants,  on  which 
it  probably  feeds.  Certain 
other  species  are  reputed  to 
exist  in  such  abundance  in  the 
soil  of  flower  and  vegetable 


FIG.  67. — The  spotted  spring- 
tail,  Papirius  maculosus,  with 
spring  extended.  (Natural  size, 
two  millimeters.) 


FIG.  68. — Young  and  adult  Le- 
pisma  sp.  from  California.  (Twice 
natural  size.) 


beds   as    to    keep    the  soil  so  constantly  disturbed  by  their 
movements  that  the  roots  cannot  hold  the  plants  firmly. 

The  other  principal  group  in  the  order,  known  as  the  Thy- 
sanura,  is  represented  in  this  country  by  three  small  families 
which  contain  but  a  few  species.  All  the  Thysanura  have  a  soft 
flattened  body  of  from  but  a  few  millimeters  to  three-fourths 
of  an  inch  in  length,  and  live  mostly  under  stones  and  logs  in 
the  soft  soil  and  humus  at  the  bases  of  tree  trunks.  A  common 
species  that  occurs  in  houses  is  known  as  the  silver-fish,  or 
fish-moth,  Lepisma  saccharina.  It  is  about  one-half  an  inch 
long  and  silvery  white  with  a  yellowish  tinge.  It  feeds 


156    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

chiefly  on  sweet  or  starchy  materials,,  sometimes  doing  real 
damage  in  libraries,  where  it  attacks  the  book  bindings.  It 
attacks  starched  clothing,  eats  the  paste  off  the  wall-paper, 
causing  it  to  loosen,  and  infests  dry  starchy  foods.  It  runs 
swiftly  and  avoids  the  light.  It  can  be  killed  by  spreading 

pyrethrum  powder  in  book  cases, 
wardrobes  and  pantries.  Another 
species,  called  the  bake-house  sil- 
ver fish,  Lepisma  domestica,  is  often 
common  about  fire  places  and 
ovens,  running  over  the  hot  metal 
and  bricks  with  surprising  immu- 
nity from  the  effects  of  the  heat. 

All  of  the  Aptera  when  hatched 
from  the  egg  very  much  resemble, 
except  in  the  matter  of  size,  the 
parent  form.  And  they  reach  the 
adult  condition  with  very  little 
change  except  that  of  a  marked 
growth  in  size. 

Order  Ephemerida. — The  Ephe- 
merida  or  May-flies,  or  lake-flies, 
are  a  small  order  of  delicate  four- 
winged  insects  which  live  in  adult 
condition  for  from  but  a  few  hours 
to  a  few  days,  varying  with  different 
species.  They  have  soft,  poorly 
developed  mouth-parts  of  biting 
type,  or  no  mouth-parts  at  all,  and 
probably  only  a  few  kinds  take  any 

food  as  adults.  The  wings  are  very  thin  and  many  veined, 
with  the  hind  wings  smaller  than  the  fore  wings,  or  even 
wholly  lost  in  a  few  species. 

The  eggs  are  dropped  into  the  water  of  ponds  or  quiet  stream 
pools,  and  the  young  which  hatch  from  them  are  soft-bodied 
flat  creatures,  called  nymphs,  which  crawl  about  on  the  bottom, 
often  on  the  undersides  of  stones.  They  have  well-developed 
biting  mouth-parts  with  sharp-pointed  mandibles.  They 


FIG.  69. — Young  (nymph) 
of  May-fly,  showing  (g)  tra- 
cheal  gills.  (Three  times 
natural  size;  after  Jenkins 
and  Kellogg.) 


THE  CLASSIFICATION  OF  INSECTS 


157 


breathe  by  means  of  delicate  leaf-like  tracheal  gills  on  the  sides 
of  the  abdomen,  and  when  ready  to  change  into  adult  condition, 
crawl  up  out  of  the  water  onto  the  bank  or  plant  stems  or  float 
to  the  surface,  and  there  quickly  cast  the  nymphal  cuticle  and 
issue  as  winged  imago.  Some  species  molt  again  after  having 
used  their  wings  a  little  while. 

The  May-flies  often  issue  from  rivers  or  lakes  in  enormous 
numbers  in  the  summer,  and  form  an  annoying  plague  to 
house-boat  dwellers  or  summer  cottagers  simply  by  their  too 
abundant  presence.  Their  dead  bodies  falling  on  the  surface 
of  the  water  are  sometimes  driven  by 
the  wind  on  the  shore  in  great  windrows. 

Order  Plecoptera. — 'The  Plecoptera, 
or  stone-flies,  are  unfamiliar  insects 
which,  like  the  May-flies,  hatch  from 
eggs  dropped  into  the  water,  and  live 
an  immature  life  of  several  months  as 
flattened  wingless  nymphs  crawling 
about  at  the  bottom.  Indeed,  the 
stone-fly  nymphs  often  live  side  by  side 
with  the  young  May-flies,  but  can  usu- 
ally be  distinguished  from  them  by  be- 
ing thicker  and  broader,  and  having 
tracheal  gills  not  leaf-like  but  composed 
of  separate  filaments  or  tufts  of  such 
filaments  rising  from  the  thoracic  seg- 
ments, one  tuft  just  behind  each  leg. 
They  cannot  live  in  stagnant  water  or 
foul  streams.  When  ready  to  change  to  the  winged  adult 
condition  the  nymphs  crawl  out  from  the  water,  the  cuticle 
splits  along  the  back,  and  the  winged  fly  issues. 

The  adult  flies  have  four  rather  large,  membranous,  many- 
veined  wings,  the  hind  ones  being  larger  than  the  front  ones. 
The  mouth-parts  are  well  developed  and  fitted  for  biting,  but 
the  food  habits  are  not  known.  About  100  species  occur  in 
North  America,  among  which  there  is  none  injurious  to  man. 
The  young  of  many  kinds  furnish  food  for  many  fishes. 
And  this  is  true  also  of  the  May-flies. 


FIG.  70.  —  Young 
(nymph)  of  stone-fly, 
from  California.  (Twice 
natural  size.) 


i58    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Order  Odonata. — -The  Odonata  are  the  familar  dragon-flies, 
devil's  darning-needles,  and  damsel-flies,  that  swoop  about  over 
ponds  and  quiet  streams,  capturing  small  flying  insects.  The 
body  is  long  and  slender,  and  the  four  wings  are  membranous, 
many-veined,  and  all  about  equal  in  size.  They  live  largely 
on  the  wing  and  are  among  the  most  rapid  and  powerful  insect 
fliers.  The  legs  are  slender  and  weak,  and  chiefly  used  to  hold 
captured  prey  up  to  the  mouth  and  for  perching.  Like  the 
May-flies  and  stone-flies,  their  young  stages  are  spent  in  water 
as  wingless,  crawling  nymphs.  Here  also  they  capture  smaller 


FIG.  71. — Adult  and  last  exuvia  of  the  white-tail  dragon-fly,  Plathemis 
trimaculata.     (Natural  size.) 


living  insects,  not  however  by  speedy  pursuit  but  by  lying  in 
wait  and  seizing  any  unwary  prey  that  may  come  within  reach 
of  the  curious  extensile  under  lip  which  is  provided  with  sharply 
toothed,  jaw-like  pincers. 

About  300  species  of  Odonata  are  known  in  North  America, 
and  2000  in  all  the  world.  All  of  them  have  beautifully 
colored  bodies,  and  many  have  the  wings  strongly  patterned 
by  conspicuous  brown  blotches  and  bands.  None  of  them  is 
injurious  to  man,  but  almost  all  may  be  considered  as  beneficial, 
because  they  are  all  destroyers  of  noxious  insects.  It  is 


THE  CLASSIFICATION  OF  INSECTS 


probable  that  dragon-flies  are  the  most  efficient  natural  remedy 
for  mosquitoes.  As  nymphs  they  destroy  many  mosquitoes 
in  their  young  or  "  wriggler"  stage,  while  as  adults  they  capture 
hosts  of  flying  mosquitoes. 


FIG.  72. — Young  (nymph)  of  a  dragon-fly,  Sympetrum  illotum. 
the  lower  lip  extended.     (Natural  size.) 


Showing 


Order  Isoptera. — -The  order  Isoplera,  termites,  or  so-called 
white  ants  (although  not  related  to  the  true  ants)  comprises  less 
than  ten  species  in  North  America,  but  is  much  better  repre- 
sented in  subtropical  and  tropical  regions.  In  equatorial 
Africa  and  South  America,  for  example,  the  termites  are  very 
important  insects  both  because  of  their  numbers  and  because 
of  their  habits.  They  have  strong  biting  mouth-parts,  and 
they  feed  chiefly  upon  dead  wood.  By  virtue  of  this  habit 
they  may  be  of  considerable  benefit  as  scavengers,  or  of  con- 
siderable harm  by  destroying  wooden  poles,  furniture,  etc. 
They  live  in  large  communities,  usually  making  their  nests 
underground  or  in  "houses"  built  of  soil  brought  up  labori- 
ously grain  by  grain  and  fastened  together  so  as  to  produce 
earthen  structures  rising  like  tents  or  pinnacles  for  several 
feet  above  the  surface  of  the  ground. 

The  communities  comprise  kings  and  queens  (males  and 
females)  provided  with  four  nearly  equal,  delicate,  membranous 


160    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

wings,  wingless  workers,  and  wingless  soldiers.  The  soldiers 
have  greatly  enlarged  mandibles  which  are  used  in  fighting 
enemies.  The  workers  are  smaller  than  soldiers  or  kings  and 
queens,  but  exist  in  larger  numbers  and  get  the  food  and  build 
the  nest  for  the  whole  community.  After  a  marriage  flight 
the  queens  find  hiding  places  in  the  ground,  break  off  their 
wings,  and  each  lays  a  few  eggs  from  which  begins  a  new 
community.  The  young  are  all  alike  when  first  hatched,  and 
only  workers  or  soldiers  develop  from  the  first  eggs.  Later 


FIG.  73. — Termite  queen,  worker  and  soldier.     (Natural  size.) 

eggs  give  birth  to  young  which  develop  wing  buds  and  after 
several  meltings  become  fully  formed  winged  individuals. 

Only  one  species,  Termes  flampes,  is  found  in  the  eastern 
states.  Its  workers  are  about  1/5  of  an  inch  long,  white 
and  soft-bodied.  The  soldiers  are  a  little  larger,  and  the 
winged  males  and  females,  which  go  from  the  nest  and  swarm 
in  the  air  in  late  spring  or  late  summer,  are  chestnut  brown  to 
blackish  and  but  little  longer  than  the  workers.  This  species 
usually  makes  its  nest  in  or  under  old  logs  or  stumps.  It 
sometimes  does  damage  by  mining  the  foundation  timbers 


THE  CLASSIFICATION  OF  INSECTS 


161 


of  houses,  and  in  the  southeastern  states  they  have  been  found 
infesting  living  plants,  particularly  orange  trees,  guava  bushes, 
sugar  cane  and  pampas  grass.  The  largest  and  most  abundant 
species,  Termopsis  augusticollis,  on  the  Pacific  coast,  makes  its 
nest  by  mining  in  dead  stumps  and  logs  and  sometimes  ruins 
telephone  and  telegraph  poles  in  this  way.  A  single  com- 
munity of  this  species  may  include  thousands  of  individuals. 

Order  Corrodentia. — -The  order  Corrodentia,   or  book-lice 
and  bark-lice,  is  composed  of  very  small  insects  most  of  which, 
composing  the  family  Psocida,  have  two  pairs  of  wings  and  a 
plump  rounded  body,  while  the  others, 
forming  the  family  Atropida,  have  no 
wings  or  only  small  wing  scales  or  buds 
and  a  flattened  body.     The  Psocidae 
are  the  bark-lice  and  are  commonly 
found  in  small  clusters  on  bark,  while 
the  Atropidae  are  the  so-called  book- 
lice,  common  in  old  books  and  on  dry 
dead  organic  matter. 

In  both  families  the  mouth-parts  are 
of  the  biting  type,  with  the  jaws  especi- 
ally strong  and  heavy  for  the  success- 
ful biting  off  and  chewing  of  hard  dried 
(food.     Atropos  divinatoria  is  the  spe- 
cies   usually   found   in   books.     It  is 
about  1/25  of  an  inch  long,  grayish- 
white,  with  slender  projecting  antennae,  and  small  eyes  look- 
ing like  distinct  black  spots  on  the  head.     It  does  not  limit 
its  feeding  to  the  paste  of  book  bindings  but  does  much  dam- 
age to  dried  insects  in  collections. 

Order  Mallophaga. — The  Mallophaga,  or  biting  bird-lice, 
compose  a  group  of  about  1500  known  species,  all  of  which 
live  as  external  parasites  on  the  bodies  of  birds  and  mammals. 
They  have  strong  biting  mouth-parts,  and  feed  exclusively  on 
the  hairs  or  feathers  of  their  host.  They  do  not,  like  the  true 
lice,  suck  blood. 

The  body  varies  from  1/25  to  1/3  of  an  inch  long,  is  wholly 
wingless  and  much  flattened.  The  insects  have  no  compound 


FIG.  74. — A  wingless 
book -louse,  Atropos  sp. 
(Much  enlarged.) 


i6a    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


eyes,  and  in  this  and  their  winglessness  show  the  degeneration 
which  a  parasitic  life  almost  always  produces.  The  eggs  are 
fastened  to  the  hairs  or  feathers,  and  the  young  undergo  little 
change  during  their  development  except  an  increase  in  size  to 
become  like  the  parents. 

Almost  every  species  of  bird  or  mammal  is  infested  by  one 
or  more  kinds  of  Mallophaga,  and  some- 
times the  host  must  suffer  much  annoy- 
ance and  even  injury  from  the  irritation 
produced  by  its  many  small  parasites. 
All  of  the  common  barnyard  birds  are 
troubled  more  or  less  by  these  biting  lice, 
and  their  presence  may  become  a  serious 
matter  in  hen-houses.  An  account  of  cer- 
tain special  Mallophagan  pests  and  of 
remedies  for  them  is  given  in  Chapter 
XXXVII. 

Order  Orthoptera. — The  order  Ortho- 
ptera  is  much  larger  than  any  of  the  other 
orders  so  far  considered,  and  includes 
many  familiar  insects,  such  as  the  grass- 
hoppers, katydids,  crickets,  cockroaches 
and  praying  mantises.  The  order  is  di- 
vided into  six  families,  of  which  three  in- 
clude all  the  well-known  singing  insects, 
except  the  cicada  or  harvest  flies.  The 
insects  in  these  three  singing  families  are 
also  the  best  known  leaping  insects,  the 
hind  legs  being  especially  long  and  strong, 
so  that  when  the  insect  is  at  rest  the 
"knee  joints"  of  these  legs  stand  up  conspicuously  above  the 
body. 

All  the  Orthoptera  have  strong  biting  mouth-parts  and  nip 
off  and  chew  their  food,  which  is  usually  green  leaves  and  stems. 
The  mantises  (family  Mantidce)  are,  however,  predaceous, 
preying  on  other  insects,  and  the  cockroaches  (family  Blattidia) 
prefer  dried  vegetable  or  animal  matter.  The  metamorphosis 
is  incomplete,  and  the  young,  which  resemble  the  parents 


FIG.  75. — A  biting 
louse  of  pigeons,  Lip- 
eurus  baculus.  (Na- 
tural size  indicated 
by  line.) 


THE  CLASSIFICATION  OF  INSECTS  163 

except  in  size  and  the  absence  of  wings,  have  the  same  feeding 
habits  and  the  same  haunts  as  the  adults.  The  name  of  the 
order  is  derived  from  the  straight-margined  parchment-like 
fore  wings  (orthos,  straight,  and  ptera,  wings)  which  are  chiefly 
used  as  covers  to  protect  the  large  membranous  hind  wings  on 
which  the  flight  function  depends.  There  are  numerous  wing- 
less species  in  the  order,  and  some  with  degenerate  short  wings 
incapable  of  flight. 

The  "  music"  which  is  made  by  the  male 'crickets,  katydids 
and  meadow-grasshoppers,  is  produced  by  the  rubbing  to- 
gether of  the  bases  of  the  f ore  <  wings  in  which  certain  veins 
are  thickened  and  roughened  so  as  to  make  effective  stridulat- 


FIG.  76. — The  American  locust,  Schistocerca  americana.     (Natural  size.) 

ing  organs.  Grasshoppers  make  sounds  when  at  rest  by 
rasping  the  inner  surface  of  the  broad  hind  legs  across  the 
outer  surface  of  the  folded  fore  wings,  and  while  in  flight  many 
of  them  make  a  loud  clacking  sound  by  striking  the  front 
margin  of  the  hind  wings  back  and  forth  past  the  hinder 
margin  of  the  thickened  fore  wings. 

Despite  the  beneficial  feeding  habits  of  the  insect-preying 
mantises,  the  Orthoptera  as  a  whole  must  be  looked  on  as  a 
seriously  injurious  group  of  insects.  Cockroaches  are  great 
pests  in  houses,  while  crickets  and  especially  grasshoppers 
work  much  injury  to  field  crops.  The  notorious  Rocky  Moun- 


164    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

tain  Locust,  Melanoplus  spretus,  which  used  to  appear 
occasionally  in  countless  numbers  in  the  grain  fields  of  the 
Mississippi  valley,  travelling  a  thousand  miles  by  a  single  flight 
from  the  Rocky  Mountain  plateau,  is  no  longer  such  a  danger, 
but  there  are  many  other  non-migratory  species  of  grass- 
hoppers which  constantly  attack  the  field  crops.  Some  of 
these  injurious  Orthoptera  are  referred  to  in  Chapter  XXXVI 
and  remedies  for  their  attacks  described. 

Order  Euplexoptera. — The  Euplexoptera,  or  earwigs,  com- 
prise a  small  number  of  insects  which  were  formerly  included 
in  the  Orthoptera.  They  are  small  brownish  or  blackish  insects 
readily  recognized  by  the  curious  forcep-like  appendages  on 
the  tip  of  the  abdomen.  They  are  either  winged  or  wingless, 
and  when  winged  have  small  thickened  wing-Covers  extending 
only  about  half  way  to  the  tip  of  the  abdomen  with  the  well- 
developed,  nearly  hemispherical  hind  wings  compactly  folded 
underneath  them.  Earwigs  are  nocturnal  in  habit,  and  feed 
by  means  of  their  biting  mouth-parts  on  ripe  fruit,  flowers 
and  other  vegetable  food.  Despite  the  name  they  have 
nothing  to  do  with  ears.  The  young  undergo  an  incomplete 
metamorphosis,  and  closely  resemble  the  parents,  except  in 
size,  from  the  time  of  their  hatching. 

Order  Hemiptera. — The  Hemiptera,  or  sucking  bugs, 
cicadas,  aphids,  scale-insects,  etc.,  compose  a  large  order  which 
includes  over  5000  species  in  North  America,  representing  a 
large  variety  of  insect  life.  Many  of  them  are  of  great  econo- 
mic importance.  Some  of  the  most  destructive  crop  pests  and 
most  discomforting  insect  scourges  of  man  and  the  domestic 
animals  belong  to  this  order.  The  chinch-bug  of  the  corn  and 
wheat  fields  of  the  Mississippi  valley,  the  tiny  sap-sucking 
aphids  or  plant-lice  and  phylloxera,  and  the  insignificant- 
looking  scale-insects  cause  annual  losses  of  millions  of  dollars 
to  American  fields,  orchards  and  vineyards. 

The  mouth-parts  in  all  the  Hemiptera  are  arranged  to  form 
a  piercing  and  sucking  beak  capable  of  taking  only  liquid 
food.  This  food  is  usually  the  sap  of  living  plants  or  the  blood 
of  living  animals.  The  wings  are  typically  four  in  number, 
although  some  species  have  but  two  wings  and  others  none. 


THE  CLASSIFICATION  OF  INSECTS 


165 


The  Hemiptera  have  an  incomplete  metamorphosis,  the  young 
at  birth  resembling  the  parents  in  most  essential  characteristics 
except  size  and  the  presence  of  wings. 

The  order  is  sub-divided  into  three  sub-orders,  one,  the 
Parasita,  composed  of  wingless  species  living  as  parasites  on 
man  and  other  mammals;  another,  the  Homoptera,  winged 
species  with  fore  and  hind  wings  of  the  same  texture  through- 
out and  usually  held  sloping  or  roof-like  over  the  back;  and 


FIG.  77. — A  water-bug,  Serphus  dilatalus.     (Natural  size.) 


another,  the  Heteroptera,  with  four  wings  held  flat  on  the  back 
when  folded  and  with  the  bases  of  the  front  wings  thickened, 
hence  the  name  of  the  order  (hemi-,  half,  ptera,  wings).  The 
Parasita  include  the  sucking  lice;  the  Hetero ptera  the  squash- 
bugs,  chinch  bugs,  water-boatmen,  assassin-bugs  and  stink- 
bugs;  while  the  Homoptera  include  the  cicada  or  harvest-flies, 
the  tree-  and  leaf-hoppers,  the  aphids,  or  plant-lice  and  the 
degenerate  scale-insects.  Some  of  the  more  injurious  species 
of  this  order  are  described  in  Chapters  XXX  to  XXXVII. 


1 66    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Order  Thysanoptera. — The  curious  little  insects  known  as 
thrips,  or  fringe- wings,  which  used  to  be  classified  with  the 
Hemiptera,  are  now  given  the  standing  of  an  independent 
small  order.  This  is  due  to  the  peculiar  character  of  their 
mouth-parts  and  feet,  and  to  the  interesting  nature  of  their 
development,  which  is  apparently  of  a  sort  of  transitional  con- 
dition between  incomplete  and  complete  metamorphosis.  The 
food  of  the  thrips  is  either  the  sap  of  living  plants  or  moist 
decaying  vegetable  matter,  especialy  wood  and  fungi.  The 
mouth  is  of  sucking  type  with  needle-like  mandibles  and 
maxillae  to  pierce  plant  tissue,  but  it  is  curiously  asymmetrical, 
the  right  mandible  being  wholly  wanting  and  the  upper  lip 
being  more  expanded  on  one  side  than  the  other.  The  feet 
have  a  small  protrusible  membranous  sac  or  bladder  at  the 
tips  instead  of  fixed  claws  or  pad.  These  tiny  sacs  probably 
fill  some  special  role  in  enabling  the  thrips  to  hold  on  to  leaves 
or  flower  surfaces. 

While  most  of  the  thrips  species  live  on  wild  plants,  a  few 
infest  fruits,  grains  and  vegetables,  and  do  much  injury. 
Among  these  are  the  onion  thrips,  wheat  thrips,  grass  thrips, 
orange  thrips  and  pear  thrips.  This  last  pest  appeared 
suddenly  in  California  a  few  years  ago,  and  since  then  has 
caused  the  loss  of  millions  of  dollars  worth  of  prunes,  apricots 
and  other  deciduous  fruits.  Several  of  the  thrips  are  described 
in  the  later  special  chapters  on  injurious  insects. 

Order  Neuroptera. — The  Neuroptera,  constituting  a  small 
order  in  point  of  numbers,  are  insects  with  biting  mouth-parts, 
and  a  metamorphosis  usually  called  complete,  but  in  which  the 
larval  stage  resembles  somewhat  the  adult  stage,  and  the  pupal 
stage  is  not  usually  undergone  as  a  wholly  immobile  chrysalid, 
but  more  often  in  a  condition  which  suggests  that  of  an  inac- 
tive larva  with  conspicuous  external  wing-pads.  This  stage 
is  usualy  passed  in  a  special  cell  or  cocoon  made  by  the  larva 
when  full  grown.  The  adults  have  four  membranous,  many- 
veined  or  so-called  "  nerve- veined "  wings,  hence  the  name  of 
the  order  (neuron,  nerve,  ptera,  wings).  The  Neuroptera 
include  seven  families  of  mostly  unfamiliar  insects,  some  very 
large,  and  others  extremely  small.  The  immature  stages  of 


THE  CLASSIFICATION  OF  INSECTS 


167 


one  family,  the  Sialida,  of  which  the  large  dobson-fly  or  hell- 
grammite  is  the  best  known  species,  are  passed  in  the  water  of 
streams  or  ponds,  but  the  members  of  all  the  other  families 
are  terrestrial  through  all  their  life.  Of  these  the  ant-lions, 
whose  larvae  make  small  pits  in  loose  soil  in  which  to  catch 
prey,  and  the  aphis-lions,  lace- winged  flies  and  snake-flies, 
whose  sharp- jawed  larvae  feed  on  such  small  defenseless  in- 
sects as  aphids  and  codling  moth  larvae,  are  more  or  less  famil- 
iar and  may  be  counted  as  beneficial  insects.  There  are  no 
seriously  injurious  insects  in  the  order. 


FIG.  78. — Pit  of  ant-lion,  and,  in  lower  right-hand  corner,  pupal  sand- 
cocoon,  from  which  adult  has  issued,  of  ant-lion,  Myrmeleon  sp. 
(About  natural  size.) 

Order  Mecoptera. — The  order  Mecoptera  includes  a  few 
little-known  insects  called  snow-fleas  and  scorpion-flies.  The 
mouth-parts  are  of  biting  type,  and  are  elongated  to  form  a  sort 
of  short,  blunt  beak.  The  metamorphosis  is  complete.  Most 
of  these  insects  are  probably  predaceous  in  habit,  feeding  on 
other  small  insects,  and  thus  perhaps  doing  good,  but  some 
take  only  animal  food  found  dead.  The  curious  snow-fleas, 
Boreus,  are  minute,  black,  leaping  creatures  that  appear  on 
snow  in  winter  time,  and  in  summer  live  on  tree  trunks  or  in 


1 68    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

moss.  The  scorpion-flies  have  four,  rather  long,  slender,  mem- 
branous wings  with  numerous  veins,  and  long  angular  legs, 
with  which  they  scramble  awkwardly  about  among  green  or 
drying  grass  leaves. 

Order  Trichoptera. — The  Trichoptera,  or  caddis-flies,  com- 
pose a  small  homogeneous  order  of  four-winged  insects  many 
of  which  look  much  like  moths.  In  fact,  there  is  little  doubt 
that  this  order  may  be  looked  on  either  as  the  direct  ancestors 
of  the  moths  and  butterflies  or  as  a  group  descended  from  such 
ancestors.  The  wings  are  membranous,  but  obscurely  colored 
by  a  covering  of  hairs  and  narrow  scales;  the  antennae  are  long 
and  slender,  and  the  legs  delicate  and  unmodified.  The  in- 
sects limit  their  flight  to  short,  uncertain  excursions  along  the 
shore  of  the  stream,  and  spend  long  hours  in  the  close  foliage 
of  the  bank.  So  far  as  observed  they  take  no  food,  although 
they  have  fairly  well-developed  mouth-parts  fitted,  apparently, 
for  lapping  up  liquids. 

The  eggs  are  dropped  into  water  and  the  aquatic  larvae 
build  protecting  cases  (hence  the  name,  case-  or  caddis-flies) 
of  little  pebbles,  sand,  or  bits  of  wood  fastened  together  by 
silken  threads.  Some  of  the  cases  can  be  carried  about  by  the 
larva  in  its  ramblings,  but  others  are  fastened  to  the  boulders 
or  rock-beds  of  the  stream.  The  larvae  are  caterpillar-like, 
with  head  and  thorax  that  project  from  the  case,  usually 
brown  and  firm- walled,  while  the  abdomen  is  soft  and  whitish. 
They  breathe  by  means  of  thread-like  tracheal  gills,  and  feed 
on  bits  of  vegetable  matter  and  probably  other  small  aquatic 
creatures.  Some  have  the  interesting  habit  of  spinning  a  tiny 
silken  net  stretched  in  such  a  way  that  its  broad  shallow  mouth 
is  directed  up-stream  so  that  the  current  may  bring  food  into 
it.  When  the  caddis-worm  is  ready  to  pupate  it  withdraws 
wholly  into  the  case  and  closes  the  opening  with  a  loose  wall  of 
stones  or  chips  and  silk.  When  ready  to  issue  the  pupa  usu- 
ally comes  out  from  the  submerged  case,  crawls  up  to  some 
support  above  the  water,  and  there  the  winged  imago  emerges. 
Some  kinds,  however,  emerge  in  the  water. 

About  500  species  of  caddis-flies  are  known  of  which  150 


THE  CLASSIFICATION  OF  INSECTS 


169 


occur  in  North  America.     None  of  them  is  injurious.     The 
larvae  of  many  species  are  eaten  by  fish. 

Order  Coleoptera. — The  great  order  of  Coleoptera,  or  bee- 
tles, is  the  largest  of  all  the  insect  groups,  and  many  of  its 
members  are  among  the  most  familiar  of  our  insect  friends  and 
enemies.  More  than  12,000  species  are  known  in  North 
America  north  of  Mexico.  They  represent  nearly  2000  genera 
grouped  into  80  families.  The  classification  of  the  Coleoptera 
is  one  of  the  most  difficult  subjects  in  the 
study  of  systematic  entomology,  and  but 
few  entomologists  know  more  than  a  few 
score  or  few  hundred  of  the  commoner 
kinds.  The  beetles  are  mostly  readily  dis- 
tinguished by  their  horny  fore  wings,  or 
elytra,  which  serve  as  protecting  covers  for 


FIG.  79.  —  Water- 
tiger,  the  larva  of  the 
predaceous  water-bee- 
tle, Dyttcus  sp.  (Nat- 
ural size.) 


FIG.  80. — The  predaceous  water-beetle,  Dy- 
ticus  sp.  pupa  and  adult.     (Natural  size.) 


the  large  membranous  hind  wings.  They  all  have  strong  bit- 
ing mouth-parts  and  a  firm  dark  chitinized  cuticle  or  outer 
body-wall.  The  body  is  usually  short  and  robust  with  its 
segments  well  fused  together.  There  is  much  variety  in  the 
character  of  the  antennas  and  feet,  and  these  differences  are 
largely  relied  on  in  classifying  beetles  into  different  families. 
The  eggs  are  laid  underground,  or  on  leaves  or  twigs  or  in 
branches  or  trunks  of  live  trees,  in  fallen  logs  or  in  decaying 


170    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

matter,  in  fresh  water,  etc.,  and  from  them  hatch  larvae,  usually 
called  grubs,  with  three  pairs  of  legs  (sometimes  wanting), 
biting  mouth-parts,  simple  eyes  and  small  antennae.  These 
larvae  may  be  predaceous,  as  water-tigers  (larvae  of  water- 
beetles),  or  plant  feeders,  as  the  larvae  of  the  long-horn  and 
leaf-beetles,  or  carrion  feeders,  as  those  of  the  burying  beetles 
and  so  on.  They  grow,  molt  several  times,  and  finally  change 
into  a  pupa  either  on  or  in  the  food,  or  very  often  in  a  rough 
cell  underground.  From  the  pupa  issues  the  fully  developed 
winged  beetle,  which  usually  has  the  same  food  habits  as  the 
larva. 

The  economic  status  of  the  order  Coleoptera  is  an  important 
one.  So  many  of  the  beetles  are  plant  feeders  and  are  such 
voracious  eaters  in  both  larval  and  adult  stages  that  the  order 
must  be  held  to  be  one  of  the  most  destructive  in  the  insect 
class.  Such  injurious  pests  as  the  Colorado  potato-beetle,  the 
round-headed  and  flat-headed  appletree  borers,  the  wire- worms 
(larvae  of  click-beetles),  the  white  grubs  of  meadows  and  lawns 
(larvae  of  June-beetles),  the  rose-chafers,  flea-beetles,  bark- 
borers,  and  fruit  and  grain  weevils  are  assuredly  enough  to 
give  the  beetles  a  bad  name.  But  there  are  good  beetles  as 
well  as  bad  ones.  The  little  lady-bird  beetles  eat  unnumbered 
hosts  of  plant-lice  and  scale-insects,  the  carrion-beetles  are 
active  scavengers,  and  the  members  of  the  predaceous  families, 
as  the  Carabids  and  tiger-beetles,  undoubtedly  kill  many  noxi- 
ous insects  by  their  general  insect-feeding  habits.  In  the  later 
chapters  on  injurious  insects  (XXX  to  XXXVII)  many  kinds 
of  beetle  pests  will  be  described. 

Order  Diptera. — The  Diptera,  or  two-winged  flies,  consti- 
tute another  large  order  of  insects,  which  are  characterized, 
first  of  all,  by  their  possession  of  but  one  pair  of  wings,  those 
of  the  meso-thoracic  segment,  the  hinder  pair  being  transformed 
into  two  short,  slender,  knob-ended  structures  called  balancers. 
These  have  a  special  nervous  equipment,  and  have  been  shown 
by  experiment  to  have  some  control  of  the  equilibrium  of  the 
fly  when  in  flight.  The  two  wings  are  membranous,  usually 
clear  and  supported  by  a  few  strong  veins.  The  mouth-parts 
show  much  variety,  and  although  no  flies  can  bite  in  the  sense 


THE  CLASSIFICATION  OF  INSECTS 


171 


of  the  chewing  and  crushing  biting  common  to  beetles,  grass- 
hoppers and  other  insects  with  jaw-like  mandibles,  some,  as 
the  mosquito,  have  elongate  mandibles,  slender  and  sharp- 
pointed,  so  that  they  act  as  lacerating  needles  to  make  punc- 
tures in  the  flesh  of  animals  or  tissues  of  plants.  Most  flies, 
however,  have  no  piercing  beak,  but,  like  the  house-fly,  lap  up 
liquid  food  with  a  curious  folding  fleshy  proboscis  which  is  the 
highly  modified  labium  or  under  lip.  They  feed  on  flower 
nectar  or  any  exposed  sweetish  liquid,  or  on  the  juices  of 
decaying  animal  or  plant  substances. 


FIG.  8 1. — Horse-fly,  Tabanus  punctifer.     (About  i|  natural  size.) 

All  the  Diptera  have  a  complete  metamorphosis,  the  young 
hatching  from  the  eggs  as  footless  and  even  headless  larvae 
(maggots,  grubs),  usually  soft  and  white,  and  in  many  cases 
taking  food  osmotically  through  the  skin.  Larvae  of  different 
kinds  of  flies  live  under  a  great  variety  of  conditions;  some  in 
water,  some  in  the  soft  tissue  of  living  plants  or  decaying 
fungi,  some  in  the  flesh  of  live  animals  or  in  carrion,  some 
underground,  feeding  on  plant  roots. 

The  pupae  of  the  more  specialized  flies  are  concealed  in  the 
thickened  and  darkened  last  larval  molt,  the  whole  puparium  or 
chrysalid  looking  much  like  an  elliptical  brown  seed.  In  some 


1 72    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

of  the  flies,  however,  as  in  the  mosquito  and  other  midges,  the 
pupal  stage  is  an  active  one  although  no  food  is  taken  during 
it.  The  life  history  is  usually  rapid  so  that  generation  after 
generation  succeeds  one  another  quickly.  Thus  it  may  be 
true,  as  an  old  proverb  says,  that  a  single  pair  of  flesh-flies 
(and  their  progeny)  will  consume  the  carcass  of  an  ox  more 
rapidly  than  a  lion. 

About  50,000  species  of  Diptera  are  known,  of  which  about 
7000  occur  in  North  America.  The  order  includes  the  familiar 
house-flies,  flesh-flies,  and  blue-bottles  of  the  dwelling  and 
stables;  the  horse-flies  and  green-heads  that  make  summer  life 
sometimes  a  burden  for  horses  and  cattle;  the  buzzing  flower- 
and  bee-flies  of  the  garden;  the  beautiful  little  pomace-flies 
with  their  brilliant  colors  and  mottled  wings,  that  swarm 
about  the  cider  press  and  fallen  and  fermented  fruit;  the  bot- 
flies, those  disgusting  pests  of  horses,  cattle,  rabbits,  rats, 
etc.;  the  fierce  robber-flies  that  prey  on  other  insects,  including 
their  own  fly  cousins;  the  midges  that  gather  in  dancing  swarms 
over  pastures  and  streams;  the  black-flies  and  punkies,  vexers 
of  trout  fishers  and  campers,  and  worst  of  all,  the  cosmopolitan 
mosquitoes,  probably  the  most  serious  insect  enemies  of  man- 
kind. A  number  of  the  specially  injurious  kinds  of  flies  are 
described  in  Chapters  XXVIII  and  XXX  to  XXXVII. 

Order  Siphonaptera. — The  fleas  are  blood-sucking  parasites 
of  birds  and  mammals  which  were  long  classified  as  a  family 
(Pulicidce)  of  the  Diptera,  being  looked  on  as  wingless  and 
otherwise  degenerate  flies.  They  are  now,  however,  given 
the  rank  of  an  independent  order.  Nearly  two  hundred  species 
of  fleas  are  known  in  the  world,  of  which  about  fifty  occur  in 
North  America.  Only  a  few  species  have  been  found  on  birds, 
the  others  on  mammals,  both  domesticated  and  wild. 

The  fleas  are  all  wingless  and  have  the  body  greatly  flattened 
laterally.  The  mouth-parts  are  composed  of  several  sharp, 
strong,  piercing  stylets  and  a  pair  of  thicker  grooved  parts  which 
can  be  held  together  to  form  a  sucking  tube.  While  the  adults 
are  more  or  less  familiar  the  young  are  rarely  seen.  The  larvae 
are  small,  slender,  white,  footless,  worm-like  grubs  which  lie 
hidden  in  cracks  and  crevices  and  live  on  dry  organic  detritus. 


THE  CLASSIFICATION  OF  INSECTS 


i73 


They  are  especially  common  in  dirty  dwellings  and  in  cat  and 
dog  houses.  With  the  common  cat-  and  dog-flea  the  larval 
life  lasts  only  one  or  two  weeks.  When  full  grown  the  larva 
usually  spins  a  thin  silken  cocoon  within  which  it  pupates. 
The  adult  flea  issues  in  a  few  days  after  pupation.  In  a  few 
species,  as  the  "chigoe"  or  "jigger"  flea  of  the  tropics,  the 
adults  burrow  into  the  skin  of  the  host,  lay  eggs  there  and  the 
young  may  pass  their  development  in  a  sort  of  tumor  caused 
by  the  burrowing  adult.  The  hen-flea  of  the  southern  States 
has  the  same  habit  of  development.  The  rat-fleas  have  been 


Human-flea,  Pulcx  irritans;  male. 


proved  to  disseminate  the  germs  of  plague  among  rats  (see 
Chapter  XXIX).  The  commonest  fleas  affecting  man  are 
the  human-flea,  Pidex  irritans,  and  the  cat-  and  dog-flea, 
Ctenocephalus  canis.  The  best  way  to  fight  them  is  to  keep 
rooms  and  the  places  where  cats  and  dogs  sleep  thoroughly 
clean.  Flea  larvae  will  not  develop  successfully  in  places 
where  they  are  often  disturbed,  hence  much  sweeping  and 
scrubbing  will  keep  them  down.  The  adult  fleas  are  very 
resistant  to  insecticides. 


i74    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Order  Lepidoptera. — Lepidoptera,  or  moths  and  butterflies, 
are  the  insects  most  favored  of  collectors  and  nature  lovers. 
The  beautiful  color  patterns,  the  graceful  flight  and  dainty 
flower-haunting  habits  and  the  interesting  metamorphosis 
during  their  development  make  them  very  attractive,  while 
the  comparative  ease  with  which  the  various  species  may  be 
determined  and  the  large  number  of  popular  as  well  as  more 
technical  books  about  them,  make  the  moths  and  butterflies, 
among  all  the  insects,  most  collected  and  studied. 

About  7000  species  are  known  in  North  America,  and  except 
for  a  few  kinds  with  wingless  females  and  a  few  other  clear- 
winged  kinds  which  have  a  superficial  likeness  to  wasps  and 
bees,  all  the  species  may  be  readily  recognized  as  moths  or 
butterflies  by  the  complete  coating  of  tiny  scales  on  the  four 
wings  both  above  and  below.  It  is  on  these  scales  that  the 
colors  and  patterns  of  the  moths  and  butterflies  depend.  The 
scales  are  very  small,  varying  from  1/350  to  1/30  of  an  inch 
in  length  and  from  the  thickness  of  a  fine  hair  to  1/60  of  an 
inch  in  breadth.  They  are  arranged  in  more  or  less  regular 
rows,  which  overlap  each  other  so  that  a  shingle-like  covering 
over  the  wing  is  produced.  On  a  large  butterfly  the  total 
number  of  scales  on  all  the  wings  may  number  more  than  a 
million.  Each  scale  is  really  a  tiny  flattened  membranous  sac 
with  a  short  stem  which  is  held  in  a  little  pit  or  pocket  in  the 
wing  membrane.  All  the  scales  are  finely  and  regularly 
striated  from  base  to  tip,  and  most  of  them  contain  a  number 
of  small  pigment  granules.  The  colors  are  produced  both 
by  the  pigment  and  by  the  complicated  reflections  caused  by 
the  striated  and  laminated  structure  of  the  scales.  On  the 
latter  condition  depend  the  irridescent  and  metallic  colors, 
such  as  the  changing  blues  and  greens,  while  on  the  presence 
of  the  pigment  depend  the  fixed  brown,  reddish  and  yellow 
colors.  The  wings  themselves  are  large  and  membranous 
and  supported  by  a  few  strong  veins.  The  fore  wings  are 
longer  and  narrower  in  proportion  to  their  length  than  the 
hind  wings,  this  condition  being  particularly  emphasized 
among  the  swift-flying  species,  such  as  the  sphinx-moths. 

The  mouth-parts  of  all  the    Lepidoptera,   except   a   few 


THE  CLASSIFICATION  OF  INSECTS  175 

primitive  species  of  moths,  are  extraordinarily  modified  so  as 
to  form  a  long,  slender,  flexible,  sucking  tube,  by  means  of  which 
flower  nectar  and  water  can  be  drunk.  This  tube  is  made  of 
the  two  elongated  maxillae,  grooved  on  their  inner  faces  and 
held,  even  locked,  together  to  form  a  perfect  tube.  Upper  lip, 
mandibles,  and  under  lip  are  either  wholly  wanting  or  reduced 
to  mere  rudiments.  Thus  no  adult  moth  nor  butterfly  can 
seriously  injure  any  plant  or  animal;  but  strongly  contrasted 
to  this  innocuousness  of  the  adults  are  the  serious  capacities 
for  mischief  of  the  larval  or  caterpillar  stage. 

From  the  eggs,  which  are  almost  always  deposited  on  the 
proper  special  food  plant,  hatch  the  well-known  worm-like 
larvae  or  caterpillars  which  are  provided  with  strong  biting 
mouth-parts.  They  proceed  at  once  to  the  serious  business  of 
voracious  eating.  The  young  caterpillar  may  eat  many  times 
its  weight  of  leaf  tissue  in  a  single  day,  and  where  the  cater- 
pillars are  abundant  they  may  quickly  defoliate  whole  shrubs 
and  trees.  The  caterpillars  are  provided  with  three  pairs  of 
jointed  thoracic  legs  and  five  pairs  of  fleshy  unjointed  abdominal 
legs,  and  can  migrate  freely  from  plant  to  plant,  thus  increasing 
their  capacity  for  harm.  When  they  are  full  grown  they  usu- 
ally burrow  into  the  ground,  spin  a  silken  cocoon,  or  seek  some 
hiding  place  in  which  to  pupate.  The  pupa  is  enclosed  in  a 
thick,  horny,  chitinized  cuticle,  and  is  wholly  inactive  and 
takes  no  food.  When  the  radical  changes  of  the  breaking 
down  of  the  larval  organs  and  the  building  of  the  new  organs 
of  the  adult  are  completed,  the  cuticle  breaks  and  the  winged 
imago  emerges. 

The  food  habits  of  the  caterpillars  make  many  of  them 
serious  pests  of  growing  crops.  Most  are  leaf  eaters,  and  all 
are  voracious  feeders,  so  that  an  abundance  of  cut-worms  or 
army-worms  or  tomato-worms  always  means  hard  times  for 
their  favorite  food  plants.  Some  kinds  do  not  eat  leaves  but 
attack  fruits,  as  that  dire  apple  pest,  the  codling-moth  larva; 
while  still  others  are  content  with  dry  organic  substances,  as 
the  larvae  of  clothes-moths,  meal-moths  and  the  like.  The  sole 
material  compensation  which  the  Lepidoptera  make  for  their 
disastrous  toll  on  all  green  things  is  the  gift  of  silk  made  by  the 


176    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

moth  species  known  as  the  mulberry  or  Chinese  silk-worm. 
This  thoroughly  domesticated  and  industrious  species  produces 
each  year  over  $100,000,000  worth  of  fine  silk.  It  can  be 
reared  with  perfect  success  in  this  country  and  made  to  produce 
large  cocoons  of  an  admirable  quality  of  silk,  but  the  cost  of 
the  labor  necessary  to  caring  for  the  larvae  through  their  long 


FIG.  83. — Silk-worms,  larvae  of  the  moth  Bombyx  mori.     (About  \  natu- 
ral size.) 

growing  period  is  so  much  higher  in  America  than  in  Italy,  or 
France,  or  the  Orient,  that  silk  cannot  be  produced  here  under 
present  conditions  to  commercial  advantage.  The  method 
of  rearing  silk-worms  is,  briefly,  as  follows. 

The  heavy,  creamy  white  moths  take  no  food,  and  most  of 
them  cannot  fly  despite  their  possession  of  well-developed 
wings,  so  degenerate  are  the  flight  muscles  from  generations 


THE  CLASSIFICATION  OF  INSECTS  177 

of  disuse.  The  eggs,  about  300,  are  laid  by  the  female  on  any 
bit  of  cloth  or  paper  provided  for  her  by  the  silk-worm  growers. 
In  the  annual  race  of  silk-worms,  i.e.,  the  one  which  produces 
but  one  generation  a  year,  the  eggs  go  through  the  winter  and 
hatch  in  the  following  spring  at  the  time  the  mulberry  trees 
begin  leafing  out.  Other  varieties  produce  two  (bivoltins), 
three  (trivoltins),  and  even  five  or  six  (multivoltins),  genera- 
tions a  year.  The  larvae,  or  "  silk- worms,"  must  be  abundantly 
fed  with  either  mulberry  or  osage  orange  leaves  from  which 
all  rain  or  dew  drops  must  be  wiped  off.  When  very  young 
they  are  fed  but  two  or  three  times  a  day,  but  later  in  their 
life  must  have  seven  or  eight  daily  meals.  They  grow  rapidly, 
and  in  most  races  are  dull  slaty  white  in  color  with  a  few  indis- 
tinct darker  markings.  They  are  very  sluggish  in  habit  and 
can  easily  be  kept  in  shallow  open  trays,  which  should  be  kept 
well  aired  and  cleaned.  The  worms  molt  every  nine  or  ten 
days,  ceasing  to  feed  for  a  day  before  each  molting  during  the 
forty-five  days  of  larval  life.  At  the  end  of  this  time  each 
worm  spins  a  dense  white  or  golden  or  pale  greenish  silken 
cocoon  which  is,  to  man,  the  silk-worm's  raison  d'etre,  but 
which  is  primarily  the  protecting  cover  for  the  defenseless  pupa. 
In  spinning  this  cocoon  the  silken  thread,  which  issues  from 
the  mouth  and  is  produced  by  the  hardening  of  a  viscous  fluid 
secreted  by  a  pair  of  long  silk  glands  stretching  far  back  in 
the  body,  is  at  first  attached  irregularly  to  near-by  objects,  so 
that  a  sort  of  loose  net  or  web  is  made;  then  the  spinning  be- 
comes more  regular,  and  by  the  end  of  three  days  the  thick, 
firm,  symmetrical,  closed  cocoon,  composed  of  a  single  con- 
tinuous silken  thread,  averaging  over  1000  feet  long,  is  com- 
pleted. Silk  growers  provide  a  loose  network  of  branches  or 
wicker  on  which  the  silk-worms  spin  their  cocoons.  Inside  the 
cocoon  the  larva  pupates,  and  if  undisturbed  the  chrysalid 
gives  up  its  damp  and  crumpled  moth  after  from  twelve  to 
fourteen  days  or  longer.  A  fluid  secreted  by  the  moth  softens 
one  end  of  the  cocoon  so  that  the  delicate  creature  can  force 
its  way  out.  But  this  is  the  happy  fate  of  only  those 
moths  which  the  grower  allows  to  issue  to  lay  eggs  for  the  next 
year's  crop.  To  produce  good  silk  the  grower  must  save  the 


1 78    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

cocoon  from  injury  by  the  moth,  so  he  kills  his  thousands  of 
pupae  by  dropping  the  cocoons  into  boiling  water  or  by 
putting  them  into  a  hot  oven.  Then,  after  cleaning  away 
the  loose  fluffy  silk  of  the  outside,  he  finds  the  beginning  of 
the  long  thread  which  makes  the  cocoon,  and  with  a  clever 
little  reeling  machine  he  unwinds,  unbroken,  its  hundreds  of 


FIG.  84. — The  luna-moth,  or  pale  empress  of  the  night,  Tropasa  luna. 
(About  f  natural  size.) 

feet  of  merchantable  silk  floss.  Or  the  cocoons  are  taken  to  a 
central  establishment  where  the  pupae  are  killed  and  the  silk 
wound  and  made  into  large  skeins  ready  to  go  to  the  cloth- 
making  mills. 

The  order  Lepidoptera  is  divided  into  three  principal  sub- 
orders, namely,  the  Rhopalocera,  or  butterflies,  which  are  day 


THE  CLASSIFICATION  OF  INSECTS  179 

fliers,  and  which  have  their  antennae  slender  and  thread-like 
with  the  tip  thickened  so  as  to  form  a  small  spindle-shaped 
club;  the  Hesperina,  or  skippers,  which  are  also  day  fliers  and 
which  have  the  antennae  slender,  and  with  slightly  expanded 
or  hooked  tip;  and  the  Heterocera,  or  moths,  most  of  which 
are  night  fliers,  and  which  have  their  antennae  variously  formed, 
either  entirely  thread-like  or  with  some  of  the  segments  pro- 
vided with  many  long  hairs  arranged  so  as  to  make  the  antennae 
look  like  a  flat  brush.  The  Heterocera  include  by  far  the 
greater  number  of  species  of  Lepidoptera,  and  many  of  the 
more  obscurely  colored  ones  are  rarely  seen.  They  vary  in 
size  from  the  small  clothes-moths  and  leaf-miners  to  the  great 
Cecropias  and  Lunas.  Colored  pictures  of  most  of  the  more 
common  kinds  of  moths  and  butterflies  can  be  found  in  nature 
books,  and  the  different  species  can  readily  be  determined  by 
referring  to  these  pictures.  A  number  of  the  species  with 
injurious  caterpillars  are  described  in  Chapters  XXX  to 
XXXVII. 

Order  Hymenoptera. — The  Hymenoptera  are  a  large  order, 
which  includes,  besides  the  popularly  known  ants,  bees  and 
wasps,  many  less  familiar  insects  showing  much  variety  in 
appearance  and  habit,  7500  species  being  found  in  this  coun- 
try alone.  Many  of  these  are  parasites,  spending  their  larval 
life  within  the  bodies  of  other  insects,  feeding  on  their  tissues 
and  finally  destroying  them.  Because  of  the  great  importance 
of  these  parasites  in  keeping  noxious  insects  in  check,  and 
because  of  the  gifts  from  the  honey-bee  and  the  innocuous 
character  of  most  of  the  other  members  of  the  order,  the 
Hymenoptera  may  be  looked  on  as  the  chief  beneficial  order  of 
insects. 

Few  generalizations  can  be  made  that  will  apply  to  all 
members  of  the  order  although  there  is  no  question  concerning 
the  true  relationship  of  all  the  kinds  of  insects  included  in  it. 
The  name  of  the  order  is  derived  from  the  clear  membranous 
condition  of  the  two  pairs  of  wings  (hymen,  membrane,  ptera, 
wings).  The  front  wings  are  larger  than  the  hind  ones  and 
all  are  provided  with  comparatively  few  branched  veins. 
The  workers  of  all  the  ant  species  are  wingless  as  are  also  the 


i8o    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

females  of  certain  wasps.  In  many  Hymenoptera  the  front 
margin  of  the  hind  wings  bears  a  series  of  small  recurved  hooks 
which,  when  the  wings  are  outspread,  fit  over  a  ridge  on  the 
hind  margin  of  the  fore  wing  thus  fastening  the  two  wings  firmly 
together.  The  mouth-parts  are  variously  modified,  but  usu- 
ally are  fitted  for  both  biting  and  lapping.  This  is  arranged  for 
by  having  the  maxillae  and  labium  more  or  less  elongated  and 
forming  a  sort  of  proboscis  for  taking  up  liquids,  while  the 
mandibles  always  retain  their  short,  strong,  j  aw-like  character. 
The  females  throughout  the  order  are  provided  either  with  a 
saw-like  or  boring  or  pricking  egg-layer  (ovipositor),  or  with 
the  same  parts  modified  to  be  a  sting. 

In  the  development  of  all  Hymenoptera  the  metamorphosis 
is  complete,  and  the  larvae  are,  more  than  in  any  other  order, 
helpless  and  dependent  for  their  food  and  safety  on  the 
special  provision  or  care  of  the  parents.  The  parasitic  species 
lay  their  eggs  either  on  or  in  the  body  of  the  insect  which  is  to 
serve  as  food  for  the  larvae,  while  the  gall-making  kinds  lay 
their  eggs  in  the  plant  tissue  on  which  their  larvae  feed.  With 
most  of  the  solitary  wasps  and  bees,  food  is  stored  up  in  the  cell 
in  which  the  egg  is  deposited,  so  that  the  larvae  on  hatching  will 
find  it  ready.  With  the  social  wasps  and  bees  and  all  the  ants, 
the  workers  bring  food  to  the  young  during  their  whole  larval 
life. 

The  Hymenoptera  may  be  roughly  divided  into  a  few  im- 
portant groups.  First,  the  saw-flies  (family  Tenthredinida) 
whose  larvae,  soft-bodied,  naked,  caterpillar-like  creatures, 
usually  with  six  to  eight  pairs  of  abdominal  legs  besides  the 
three  pairs  of  thoracic  legs,  are  called  slugs.  Common  kinds 
are  the  current-slug,  rose-slug,  larch-slug  and  others,  which  do 
considerable  damage  by  eating  away  the  soft  tissues  leaving 
only  the  veins,  thus  making  " skeletons"  of  the  leaves  of  their 
food  plants.  The  saw-flies  compose  a  large  family,  600  species 
being  known  in  this  country,  but  the  adults  are  rarely  seen  by 
the  general  observer. 

Second,  the  great  group  of  parasites  comprising  several 
families  (Ichneumonidce,  Braconidce,  Chalcididce,  Proctotrypida, 
and  others),  and  including  species  varying  in  size  from  the 


THE  CLASSIFICATION  OF  INSECTS 


181 


smallest  insects  known  to  others  two  inches  or  more  in  length. 
Some  of  these  minute  parasites  lay  their  eggs  within  the  eggs  of 
other  insects,  and  their  larvae  live  their  whole  lives  in  the  con- 
tents of  these  host  eggs,  but  most  Hymenopterous  parasites 
deposit  their  eggs  on  the  skin  of  the  larvae  or  nymphs  of  other 
insects,  especially  on  caterpillars.  The  parasite  larvae,  on 
hatching,  bore  their  way  through  the  skin  into  the  host  body 
and  remain  there,  feeding  on  the  blood  lymph  and  perhaps  on 
other  body  tissues.  The  host  dies,  but 
usually  not  until  the  parasites  have  com- 
pleted their  larval  life  and  have  changed 
to  pupae  either  within  the  host's  body,  or 
have  issued  from  it  and  pupated  outside. 
Parasitized  caterpillars  are  often  able  to 
pupate,  but  from  their  pupa  there  issues, 
not  a  moth  or  butterfly,  but  many  of  the 
little  four-winged  parasites.  These  fly 
freely  about,  mate,  and  then  deposit  their 
eggs  on  the  body  of  other  hosts. 
,  A  few  members  of  this  group  are  not 
parasites  but  gall-makers.  Among  these 
an  important  kind  is  the  curious  small  fig- 
wasp  (Blastophaga)  by  which  the  Smyrna 
figs  are  cross-pollinated  and  made  to  set 
seed  and  thus  to  become  especially  palata- 
ble. The  fig- wasp  has  been  introduced  from  Asia  Minor  into 
California,  and  has  greatly  added  to  the  value  of  California 
figs. 

Third,  the  family  Cynipida  or  gall-flies,  some  of  which  are 
parasites,  but  most  of  which  thrust  their  eggs,  by  means  of  a 
sharp  ovipositor,  into  the  leaves  or  green  stems  of  oaks,  roses 
and  a  few  other  plants,  so  that  the  hatching  larvae  find  them- 
selves surrounded  by  rich  plant  food.  The  presence  of  the 
larva  stimulates  the  plant  to  a  vigorous  production  of  new 
tissue  about  it,  which  takes  on  the  form  of  a  gall  of  definite 
shape.  These  galls  are  different  for  different  species  of  gall- 
flies, and  for  different  species  of  plants,  and  present  a  host  of 
curious  shapes.  Some  look  like  tiny  seeds  or  papillae  on  the 


FIG.  85. — Ichneu- 
mon fly,  Pimpla  con- 
qidsitor,  laying  egg  in 
cocoon  of  American 
tent-caterpillar  moth. 
(About  natural  size; 
after  Fiske.) 


i82    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

leaf  or  stem,  while  others,  as  the  giant  oak-gall  of  California, 
are  as  large  as  one's  fist.  The  gall-fly  larvae  lie  in  the  middle 
of  the  galls  feeding  on  the  abundant  plant  juice  and  pupating 
there  in  the  autumn  when  the  active  plant  growth  ceases.  The 
gall-flies  issue  in  the  following  spring,  biting  their  way  out  of 
the  gall  by  means  of  their  stout  jaws. 

The  fourth,  fifth  and  sixth  groups  of  Hymenoptera  are  the 
wasps,  bees  and  ants.  They  are  treated  in  the  following 
chapter. 


CHAPTER  XVIII 

INSECTS    (Continued):  WASPS,   ANTS,     THE  HONEY- 
BEE AND  OTHER  BEES 

Wasps. — The  wasps  are  divided  into  two  groups,  viz.,  the 
solitary  or  digger  wasps  (superfamily  Sphecina),  and  the  social 
wasps  (super-family  Vespina).  The  Sphecina,  as  represented 
in  North  America,  include  a  dozen  or  more  families,  while  the 
Vespina  include  but  three,  but  these  latter  wasps,  or  a  few  of 
them,  the  hornets  and  yellow- jackets,  are  more  often  seen  and 
much  better  known  popularly  than  the  solitary  wasps.  Among 
the  solitary  bees  each  female  makes  a  simple  nest,  usually  a 
short  burrow  in  the  ground  or  in  a  plant  stem  (in  the  case  of  a 


FIG.  86. — Digger-wasp,  Ammophila,  putting  inch-worm  into  nest-burrow. 
(From  life;  natural  size.) 

few  parasitic  kinds  the  wasp  makes  no  special  nest  at  all),  lays 
one  or  more  eggs  in  it,  stores  it  with  food  for  the  hatching  larva?, 
and  closes  it  up.  This  food  is  usually  other  insects  or  spiders 
stung  to  death  or,  more  commonly,  stung  in  such  a  way  as  not 
to  kill  but  paralyze  the  prey.  When  the  wasp  larvae  hatch 
they  find  their  food  all  ready  for  them,  devour  it  slowly  as  they 
grow,  pupate  in  the  nest  burrow,  and  finally  issue  as  full 
fledged  wasps. 

The  social  wasps  live,  as  is  well  known,  in  large  communities 
composed  of  an  active  egg-laying  female  or  queen,  a  few  males 

183 


i84    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

or  drones,  and  many  infertile  females,  or  workers.  A  small 
nest  is  made  in  the  spring  out  of  chewed  old  wood  mixed  with 
saliva  so  as  to  form  "wasp-paper,"  by  a  queen  that  has  mated 
in  the  autumn  before  and  passed  the  winter  solitarily  in  hiding. 
In  this  little  "queen  nest"  she  lays  a  few  eggs,  brings  food  to 
the  hatching  larvae  until  they  change  to  pupae  in  their  cells, 
and  then  awaits  their  issuance.  They  issue  as  workers,  and 
immediately  enlarge  the  nest,  making  more  paper  combs  and 
cells,  in  which  the  queen  lays  more  eggs.  The  workers  bring 
food,  which  is  killed  and  masticated  insects,  and  care  for  the 

young,   which    develop    into 
more  workers.    Thus  the  com- 
munity,    or     really     family, 
grows  through   the    summer, 
till  it  may  contain  many  hun- 
dred individuals.     In  the  late 
summer  males  and  fertile  fe- 
males are  produced,  and  then 
FIG.  87—  Two  workers  of  the      with  the  oncoming  of  winter 
SP'    <Fr°m      ^e    workers  and  males  and 
many  of  the  females  die,  leav- 
ing a  few  mated  females  to  pass  the  winter  and  begin  new 
colonies  in  the  spring.     Thus  the  social  wasp  communities 
break  down  and  are  rebuilt  annually. 

Bees. — This  is  also  the  case  with  the  communities  of  bumble 
bees,  which  are  the  simplest  kind  of  social  bees.  There  are 
among  the  bees  solitary  kinds  also,  with  the  same  general 
manner  of  life  of  the  solitary  wasps,  except  that  the  food  col- 
lected and  stored  for  the  young  is  never  killed  or  paralyzed 
insects  but  always  flower  nectar  and  pollen  mixed.  This  is 
also  the  kind  of  food  brought  by  the  bumble-bees  for  their 
larvae. 

Among  the  bees  there  is  however  another  and  more  special- 
ized type  of  social  kind.  This  type  is  represented  in  America 
by  a  single  species,  the  honey-bee  or  hive-bee,  Apis  mellifica, 
which  is  not  a  native  insect  but  one  introduced  long  ago  from 
Europe.  With  this  bee  the  community  does  not  break  down 
annually  but  persists,  under  favorable  conditions,  indefinitely. 


WASPS,  ANTS  AND  BEES 


The  hive-bee  has  long  been  a  domesticated  species  of  animal, 
and  several  different  varieties  or  races  of  it  have  been  created 
by  artificial  selection,  the  more  familiar  ones  being  the  German 
or  black  race,  the  Italian  or  amber  race,  and  Carniolan  or 
striped  race.  As  the  life  of  the  honey-bee  is  not  only  one  of 
the  most  interesting  of  all  animal  lives,  but  is  one  which  the 
economic  zoologist  needs  especially  to  know,  we  give  in  the 
following  pages  a  rather  detailed  ac- 
count of  the  natural  history  of  the 
honey-bee,  mostly  taken  from  Chapter 
XV  of  "American  Insects,"  by  the  sen- 
ior author. 

The  Honey-bee. — A  community  of 
the  hive-bee,  which  may  live,  of  course, 
not  in  a  hive  at  all,  but  in  a  hollow 
tree,  as  undoubtedly  was  the  habit  of 
the  species  in  wild  state  (the  "bee- 
trees"  of  America,  however,  are  inhab- 
ited by  bee  colonies  which  have  swarmed 
away  from  domesticated  ones  and  are 
only  wild  by  virtue  of  escaping  from 
the  slave-yards  of  their  human  mas- 
ters), consists  normally  of  about  10,000 
(winter)  to  50,000  (summer)  individuals, 
of  which  one  is  a  fertile  female,  the 
queen;  a  few  score  to  several  hundred  are 
males,  the  drones;  and  the  rest  are  infer- 
tile females,  the  workers.  These  three 
kinds  of  individuals  are  readily  distinguishable  by  structural 
characters.  The  queen  has  a  slender  abdomen  one-half  longer 
than  that  of  a  worker,  she  has  no  wax-plates  on  the  underside 
of  the  abdominal  segments,  and  no  transverse  series  of  comb- 
like  hairs,  the  planta,  on  the  underside  of  the  broad  first  tarsal 
segment  of  the  hind  feet,  and  no  pollen-basket  on  the  outer 
surface  of  the  hind  tibia.  The  drones,  males,  have  a  heavy 
broad  body  excessively  hairy  on  the  thorax,  and  lack  pollen- 
basket,  planta,  wax-plates,  and  other  special  structures  of  the 
workers.  The  workers  are  smaller  than  queen  or  drones,  and 


FIG.  88.— Bumble-bee 
at  clover  blossom. 
(From  life;  natural  size.) 


1 86    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

possess  certain  special  structures  or  body  modifications  to 
enable  them  to  perform  certain  special  functions  connected 
with  their  performance  of  the  various  industries  characteristic 
of  the  species.  These  special  structures  will  be  described  in 
some  detail  later  when  the  various  special  industries  are  par- 
ticularly considered.  In  internal  organization  the  workers 
differ  from  the  queen  in  having  the  ovaries  rudimentary,  so 
that  only  in  exceptional  cases  can  workers  produce  fertile 
eggs. 

In  functions  the  three  castes  differ  as  they  do  in  the  social 
wasps  and  the  bumble-bees,  only  more  constantly;  that  is,  the 

queen  lays  the  eggs,  never,  as  with 
the  bumble-bees  and  social  wasps, 
doing  any  food-gathering  or  nest- 
building;  the  males  act  simply  as 
consorts  for  the  queen,  which 
means  that  only  one  of  every  thou- 
sand, perhaps,  performs  any  neces- 
»  jg  sary  function  at  all  in  the  commu- 

...     nal  economy;   the  workers  build 
FIG.    89— Honey-bee,    Apis  /  ' 

mellifica.  a,  Queen;  b,  drone;  c,  brood-  and  food-cells,  gather,  pre- 
worker.  (About  jnatural  size.)  pare  and  store  food,  feed  and 

otherwise  care  for  the  young,  re- 
pair, clean,  ventilate,  and  warm  the  hive,  guard  the  entrance 
and  repel  invaders,  feed  the  queen,  control  the  production  of 
new  queens,  and,  with  the  aid  of  a  queen,  distribute  the  spe- 
cies, founding  new  communities,  by  swarming. 

The  life  history  of  a  community  is  as  follows:  A  "swarm" 
consisting  of  a  queen  and  a  number  of  workers  (from  two  to 
twenty  thousand  or  more),  issues  from  a  community  nest  and 
finds,  through  the  efforts  of  a  few  of  the  workers,  a  place  for  a 
new  nest.  This  is  some  sheltered  hollow  place,  usually,  through 
the  intervention  of  the  bee-keeper,  another  hive.  Taking 
possession  of  this  new  nesting-place,  the  workers  immediately 
begin  to  secrete  wax  and  to  build  "comb,"  i.e.,  double-tiered 
layers  of  waxen  cells,  usually  as  "curtains"  or  plates  hanging 
down  from  the  ceiling  of  the  nest.  The  bee-keepers  supply 
artificially  made  "foundations"  or  beginnings  of  these  curtains 


WASPS,  ANTS  AND  BEES  187 

in  vertical  frames  set  parallel  and  lengthwise  of  the  hive,  so 
that  the  combs  will  be  built  symmetrically  and  conveniently 
for  the  bee-keeper's  handling.  In  many  of  these  cells  the 
queen,  which  has  received  the  fertilizing  sperm-cells  from  a 
male  during  a  mating  flight  high  in  the  air,  lays  fertilized  eggs, 
one  at  the  bottom  of  each  cell.  In  other  cells,  pollen  and 
nectar  brought  by  workers  are  stored  for  food.  In  three  days 
the  eggs  hatch,  the  tiny  larvae  being  footless,  white,  soft-bodied 
helpless  grubs.  They  are  fed  at  first  exclusively  with  "bee- 
jelly,  "a  highly  nutritious,  "pre-digested"  substance  elaborated 
in  the  bodies  of  the  nurse  workers  and  regurgitated  by  them 
into  the  mouths  of  the  larvae.  After  a  couple  of  days  of  feeding 
with  this  substance,  the  larvae  are  fed,  in  addition  to  bee-jelly, 
pollen  and  honey  taken  by  the  nurse  from  the  cells  stored  with 
these  food-substances.  After  three  days  of  this  mixed  feeding, 
the  larvae  having  grown  so  as  to  fill  half  or  two-thirds  of  the  cell, 
lying  curled  in  it,  a  small  mass  of  mixed  pollen  and  honey  is 
put  into  each  cell,  which  is  then  capped,  i.e.,  sealed  over  with  a 
thin  layer  of  wax.  The  larva  feeds  itself  for  a  day  or  two 
longer  on  the  "bee-bread"  and  then  pupates  in  the  cell.  The 
quiescent  non-feeding  pupal  stage  lasts  for  thirteen  days,  when 
the  fully  developed  bee  issues  from  the  thin  pupal  cuticle, 
gnaws  away  the  wax  cap  and  emerges  from  the  cell.  For  from 
ten  days  to  two  weeks  the  bee  does  not  leave  the  hive;  it  busies 
itself  with  indoor  work,  particularly  nurse  work,  the  feeding 
and  care  of  the  young.  Then  it  takes  its  place  with  the  fully 
competent  bees,  makes  foraging  expeditions  or  undertakes 
capably  any  other  of  the  varied  industries  of  the  worker 
caste. 

After  numerous  workers  have  been  added  to  the  community, 
egg-laying  by  the  queen  going  on  constantly,  so  that  the  young 
come  to  maturity,  not  in  broods,  but  consecutively,  day  after 
day,  certain  hexagonal  cells  of  plainly  larger  diameter  are  made 
by  the  comb-building  workers,  and  in  these  the  queen  lays 
unfertilized  eggs.  This  extraordinary  capacity  for  producing 
either  fertilized  or  unfertilized  eggs,  as  demanded,  depends 
upon  the  queen's  control  of  the  male  fertilizing  cells  held  in  the 
spermatheca.  This  reservoir  of  fertilizing  cells  can  be  kept 


1 88    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

open  as  eggs  pass  down  the  oviduct  and  by  it  on  their  way  out 
of  the  body,  thus  allowing  the  spermatozoids  to  swim  out, 
penetrate  (through  the  micropyle  in  the  egg-envelopes)  and 
fertilize  the  eggs,  or  it  may  be  kept  closed,  preventing  the 
issuance  of  the  spermatozoids  and,  consequently,  fertilization. 
From  the  unfertilized  eggs  laid  in  the  larger  cells  hatch  larvae 
which  are  fed  and  cared  for  in  the  same  way  as  the  worker 
larvae,  but  which  require  six  days  for  full  growth,  the  pupal 
stage  lasting  fifteen  days.  When  finally  the  fully  developed 
bees  issue  from  these  cells  it  will  be  found  that  all  are  males 
(drones).  This  parthenogenetic  production  of  drones,  dis- 
covered about  1840  by  Dzierzon,  and  long  accepted  as  proved, 
was  recently  questioned  by  Dickel  and  one  or  two  other  natu- 
ralists and  was  therefore  reinvestigated  by  Petrunkewitsch 
and  others,  with  the  result  of  confirming,  on  new  evidence, 
and  by  new  methods  of  investigation,  the  declarations  of  the 
discoverer  of  the  fact. 

If,  now,  the  bee  community  has  increased  so  largely  in  num- 
bers that  its  quarters  begin  to  be  insufficient  for  further  ex- 
pansion, excited  groups  of  workers  will  be  seen  tearing  down 
certain  cells  and  replacing  them  by  a  new  giant  cell  which  is 
usually  built  up  around  one  of  the  fertilized  eggs  laid  in  a 
small  hexagonal  cell.  The  egg  hatches  before  the  cell  is  fin- 
ished, and  the  larva  lies  in  the  large  open  cavity  of  the  growing 
cell,  on  which  numerous  nurses  are  in  constant  attendance. 
Often  several  of  these  unusual  giant  cells  may  be  built  at  one 
time.  The  larva  which  hatches  from  the  fertilized  egg  in  one 
of  these  cells  is  fed  the  nutritious  bee-jelly  through  all  of  its 
life,  little  or  no  pollen  or  honey  being  given  it.  When  the 
larva  is  five  days  old  a  quantity  of  the  milky  semi-fluid  jelly 
is  put  into  the  cell,  which  is  then  capped,  the  opening  being  at 
the  bottom  of  the  hanging,  nut-shaped  cell,  and  in  only  seven 
days  more  the  fully  developed  bee  issues.  This  bee  is  a  queen. 
Very  rarely  a  worker  and  not  a  queen  issues  from  a  queen-cell. 
That  is,  a  larva  hatching  from  a  fertilized  egg  laid  by  the 
queen  in  a  small  hexagonal  cell,  if  fed  bee- jelly  for  two  or  three 
days  and  then  pollen  and  honey,  will  develop  into  a  worker; 
that  larva  from  the  same  egg  if  fed  bee-jelly  all  its  life,  and 


WASPS,  ANTS  AND  BEES  189 

reared  in  a  large  roomy  cell,  will  develop  into  a  queen.  The 
differences  between  a  queen  honey-bee  and  a  worker  honey-bee, 
both  structural  and  physiological,  are  as  already  pointed  out, 
conspicuous.  The  influence  of  a  varying  food-supply  is  some- 
thing mysteriously  potent,  and  this  case  of  the  queen  bee 
gives  great  comfort  to  those  biologists  who  believe  that  the 
external  or  extrinsic  factors  surrounding  an  animal  during 
development  have  much  influence  in  determining  its  outcome. 

As  there  is  by  immemorial  honey-bee  tradition  but  one  queen 
in  a  community  at  one  time,  when  new  queens  issue  from  the 
great  cells  something  has  to  happen.  This  may  be  one  of  three 
things;  either  the  old  and  new  queens  battle  to  death,  and  it  is 
believed  that  in  such  battles  only  does  a  queen  bee  ever  use  her 
sting,  or  the  workers  interfere  and  kill  either  the  old  or  the  new 
queen  by  "balling"  her  (gathering  in  a  tight  suffocating  mass 
about  her),  or  either  old  (usually  old)  or  new  queen  leaves  the 
hive  with  a  swarm,  and  a  new  community  is  founded.  If 
several  new  queens  are  to  issue,  the  workers  usually,  by  thick- 
ening the  outside  walls  of  one  or  more  of  the  cells,  compel  the 
issuing  to  be  successive  and  not  simultaneous.  This  results 
in  a  series  of  royal  battles,  or  a  series  of  swarmings,  or  a  combi- 
nation of  the  two.  A  queen  ready  to  issue  from  a  cell  makes 
a  curious  piping  audible  some  yards  from  the  hive,  which  is 
answered  by  a  louder  piping,  or  trumpeting,  from  the  old 
queen.  At  these  times  there  is  great  excitement  in  the  hive, 
as  indeed  there  is  during  all  of  the  queen-raising  season. 

The  swarming  out,  it  is  apparent,  does  not  break  up  the  old 
community;  in  fact  only  accident,  or  the  successful  attacks  of 
such  insidious  enemies  as  the  bee-moth,  and  various  contagious 
diseases,  break  up  the  parent  colony.  In  this  respect  is  to  be 
noted  an  important  difference  between  the  other  social  bees 
and  wasps  with  their  communities  annually  destroyed  and 
refounded,  and  the  honey-bee  with  its  persistent  one.  Of 
course  workers  die  and  so  do  drones  and  queens.  The  tireless 
workers  which  hatch  and  labor  in  the  spring  and  summer 
months  rarely  live  more  than  six  or  eight  weeks,  while  the 
workers  born  in  the  late  autumn  and  remaining  quietly  in  the 
shelter  of  the  hive  through  the  winter  live  for  several  months. 


igo    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Queens  live,  usually,  if  no  accident  befalls,  two  or  three  years; 
an  age  of  four  or  five  years  is  occasionally  attained.  Most  of 
the  drones  in  each  community  either  die  naturally  before  win- 
ter conies  or  are  killed  by  the  workers.  Feeble  workers  and 
larvae  and  pupae  are  also  sometimes  killed  just  before  winter, 
if  the  food-stores  which  are  to  carry  the  community  through 
the  long  flowerless  season  are  for  any  reason  not  likely  to  prove 
sufficient  for  so  large  a  number  of  individuals.  In  all  these 
matters,  that  is,  the  making  of  queens  and  when,  the  swarming 
out  and  when,  and  the  reduction  of  the  community  to  safe 
winter  numbers,  the  decision  is  made  by  the  workers  and  not 
the  queen.  The  queen  is  not  a  ruler;  she  is  the  mother,  or, 
better,  simply  the  egg-layer  for  the  whole  community. 

The  drones,  we  have  seen,  have  one  particular  function  to 
perform  in  the  community  life,  the  queen  another  single  partic- 
ular function;  but  the  workers  have  numerous  varied  perform- 
ances to  achieve  if  the  community  shall  live  successfully.  It 
might  be  expected  by  analogous  conditions  elsewhere  existing 
in  animal  life,  that  with  the  division  of  labor  in  the  honey-bee 
economy  there  should  be  a  corresponding  differentiation  of 
structure  or  polymorphism  inside  the  species.  This-  polymor- 
phism or  existence  of  structurally  different  kinds  of  individuals 
occurs  in  bees  only  to  the  extent  already  pointed  out;  there  are 
three  kinds  of  individuals:  the  queens,  with  a  special  function, 
the  drones  with  a  single  special  function,  and  the  workers,  each 
capable  of  performing,  and,  for  the  time  of  the  performance, 
doing  it  exclusively,  any  of  the  varied  industries  necessary  to 
the  community  life.  All  worker  honey-bees  are  alike,  each 
possessing  all  the  special  structural  specializations,  as  pollen- 
basket,  wax-plates,  wax-shears,  trowel-like  jaws,  etc.  which 
have  been  developed  for  the  special  performance  of  particular 
industries.  In  some  other  communal  insects  a  differentiation 
or  polymorphism  among  the  workers  exists;  many  ant  species 
have  two  and  even  three  kinds  of  workers,  the  termites  have 
soldiers  as  well  as  workers,  etc.  We  purpose  now  to  describe 
briefly  each  of  the  principal  special  industries  achieved  by  the 
workers,  at  the  same  time  describing  the  structural  specializa- 
tion connected  with  each  of  these  industries. 


WASPS,  ANTS  AND  BEES 


191 


The  wax  produced  by  the  workers  is  a  secretion  which  issues 
as  a  liquid,  soon  hardening,  from  pairs  of  thin  five-sided  plates, 
one  pair  on  the  ventral  surface  of  each  of  the  last  four  abdomi- 
nal segments.  It  is  secreted  by  modified  cells  of  the  skin, 
lying  under  the  chitinized  cuticle  of  the  plates,  and  oozes  out 
through  fine  pores  in  the  plates.  To  produce  it  certain  workers 
eat  a  large  amount  of  honey,  then  massing  together  form  a 
curtain  or  festoon  hanging  down  from  the  ceiling  of  the  hive 
or  frame,  and  increase  the  temperature  of  their  bodies  by  some 
strong  internal  exertion;  after  the  lapse  of  several  hours,  some- 
times indeed  of  two  or  three  days,  fine,  thin,  glistening,  nearly 
transparent  scales  of  wax  appear  on  the 
"  wax-plates. "  These  wax-scales  continue 
to  increase  in  area  and  soon  project  beyond 
the  margin  of  the  segment,  when  they 
either  fall  off  or  are  plucked  off  by  the 
wax-producing  worker.  They  are  then 
taken  in  the  mouth,  sometimes  chewed 
and  mixed  with  some  saliva,  and  carried 
to  the  seat  of  the  comb-building  operation. 
Here  the  wax  is  pressed  against  the  frame 
roof  (or  artificial  foundation)  and  by  means 
of  the  trowel-like  mandibles  moulded  into 
the  familiar  hexagonal  cells;  each  comb  be- 
ing composed  of  a  double  layer  of  these 
cells,  a  common  partition  serving  as  base 
or  bottom  of  each  tier.  Although  most 
bee  books  speak  rather  glibly  of  the  comb-building  operations, 
many  of  its  details  are  still  undetermined.  In  building  cells 
for  storing  honey,  new  wax  is  almost  exclusively  used;  for 
brood-cells,  old  wax  and  wax  mixed  with  pollen  may  be  used. 
Any  comb  or  part  of  a  comb  not  needed  is  torn  down  and 
the  wax  used  to  build  other  comb  or  to  cap  cells. 

The  seeking  and  collection  of  pollen  and  honey  is  not  under- 
taken by  a  bee  until  from  ten  to  fifteen  days  after  its  emergence 
from  the  pupal  cuticle,  these  first  days  being  spent  in  the  hive 
at  nurse  or  other  indoor  work.  Then  short  orienting  flights 
begin  to  be  made,  and  soon  the  long-distance  flights  (a  mile  or 


FIG.  90. — Ventral 
view  of  abdomen  of 
honey-bee  worker, 
showing  wax  plates. 
(About  3  times  nat- 
ural size.) 


ig  2    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

more  sometimes),  which  are  often  necessary  for  successful 
foraging,  are  undertaken.  The  pollen  is  taken  up  or  brushed 
off  from  the  ripe  anthers  of  the  flowers  with  the  mouth-parts, 
fore  legs  or  ventral  body-wall,  the  pollen-grains  being  readily 
entangled  in  the  numerous  branching  hairs,  and  then,  by 
clever  manipulation  of  the  fore,  middle,  and  hind  legs  aided  by 
special  pollen  brushes  (plantae)  on  the  inner  side  of  the  first 
tarsal  segments  of  the  hind  feet,  transferred  and  packed  into 
the  pollen-baskets,  one  on  the  outer  face  of  each  hind  tibia.  A 
forager  loaded  with  pollen  returns  to  the  hive,  and,  seeking  an 
empty  cell  near  the  brood-cells,  stands  over  it  and  with  her 
hind  legs  partly  in  it,  thrusts  off  the  two  masses  with  the 
aid  of  the  middle  legs  (the  spurs  of  the  middle  tibiae  being 
apparently  often  used  as  pries).  This  pollen  is  tamped 
down  in  the  cell  by  inside  workers  and  receives  no  further 
manipulation. 

The  "honey"  which  is  collected  by  the  foragers  is  not  yet 
bee-honey,  but  is  nectar  of  flowers,  too  watery  and  too  likely 
not  to  "keep"  to  be  stored  in  the  cells  without  further  treat- 
ment. It  is  sucked  and  lapped  up  by  the  complicated  elongate 
flexible  mouth-proboscis,  swallowed  into  the  fore-stomach  or 
honey-sac,  and  carried  in  this  to  the  hive.  Bees  have  been 
seen  to  exude  drops  of  water  on  their  return  flight  when  honey- 
laden,  and  it  is  possible  that  it  comes  from  the  nectar  in  the 
honey-stomach.  At  any  rate  some  10  or  12  per  cent,  of 
the  water  content  of  the  nectar  has  to  be  evaporated  before 
this  nectar  becomes  honey.  When  the  foraging  worker  with 
honey-sac  full  returns  to  the  hive  it  regurgitates  its  nectar 
either  into  the  mouth  of  another  bee  or  into  a  clean  (new  wax) 
cell,  usually  near  the  margin  of  the  comb.  At  the  bottom  of 
the  honey-sac  is  the  so-called  stomach-mouth,  a  little  pea-like 
protuberance  with  two  cross-slits,  making  four  lips.  These 
lips  can  be  opened  or  closed  voluntarily;  if  the  bee  drinking 
nectar  wishes  to  bring  it  back  to  the  hive  to  store  it,  she  keeps 
them  closed,  thus  making  a  sac  of  the  honey-stomach,  open 
only  through  the  mouth;  whenever  she  wishes  to  feed  herself 
she  opens  them,  thus  allowing  the  honey  or  pollen  to  pass  on 
into  the  true  or  digesting  stomach.  This  arrangement  also 


193 

permits  of  the  regurgitation  of  the  bee-jelly  or  bee-milk  (fed 
the  larvae  by  the  nurse  workers),  which  is  believed  to  be  pre- 
pared in  the  true  stomach,  pressed  past  the  lips  forward  into 
the  honey-stomach  and  on  through  the  esophagus  into  the 
mouth. 

When  the  nectar  is  put  into  the  honey-cells  it  has  still  to 
have  much  water  evaporated  from  it.  To  accomplish  this  an 
effective  system  of  ventilation  is  set  up  in  the  hive,  so  that 
air-currents  pass  constantly  over  the  open  nectar-containing 
cells;  moreover,  by  the  very  vigor  of  this  activity  on  the 
part  of  the  bees  the  temperature  of  their  bodies  is  raised; 
by  radiation  of  heat  from  the  bodies  the  temperature  in  the 
hive  is  sensibly  increased,  and  the  currents  of  warm  air  soon 
carry  off  the  excess  water.  To  make  the  honey  "keep,"  that 
is,  to  make  it  antiseptic,  formic  acid  is  added  to  it,  probably 
from  glands  in  the  head  whose  secretions  distinctly  show  its 
presence.  It  is  just  possible  that  the  formic  acid  is  supplied 
by  the  poison-sacs,  the  poison  introduced  by  the  bee's  sting 
being  largely  composed  of  formic  acid.  But  it  is  much  more 
probable  that  at  the  time  of  the  regurgitation  of  the  nectar 
from  the  honey-stomach  through  the  mouth  the  formic-acid 
secretions  from  the  head-glands  are  mixed  with  it. 

Nectar  for  honey-making  is  obtained  by  bees  from  a  great 
many  different  plants,  but  that  from  some  makes  honey  better, 
to  our  taste,  than  that  from  others.  Among  the  most  impor- 
tant producers  of  the  best  honey  in  the  east  and  north  are  white 
clover,  basswood,  buckwheat,  and  the  fruit  trees  and  small 
fruits;  in  the  middle  states  are  the  tulip  tree,  sorrel- tree,  sweet 
clover,  and  alfalfa;  in  the  south  are  the  mangrove,  cabbage- 
and  saw-palmettos,  orange  trees  and  sorrel- tree ;  while  in 
the  west  are  alfalfa  and  white  sage. 

Besides  pollen  and  nectar,  two  other  substances  are  collected 
and  brought  to  the  hive  by  the  foraging  workers.  At  some 
seasons  of  the  year  when  many  larvae  are  being  reared,  and  the 
supply  of  water  derived  by  condensation  of  the  moisture  in 
the  warm  hive  atmosphere  as  this  air  strikes  the  cooler  hive- 
walls  is  insufficient,  the  workers  drink  up  dew  from  leaves,  or 
water  from  puddles,  which  they  hold  in  the  honey-sac  and  bring 


i94    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

to  the  hive,  regurgitating  it  into  the  thirsty  larval  mouths. 
For  the  filling  in  of  crevices,  the  stopping  up  of  holes,  the  fasten- 
ing together  of  loose  parts,  etc.,  the  bees  use  a  substance 
called  propolis,  which  is  made  of  the  resinous  exudations  of 
various  plants.  This  propolis  is  collected  and  packed  into 
the  pollen-baskets  as  pollen  is  and  brought  in  by  the  foragers. 
Some  of  our  bees,  needing  propolis,  discovered  a  house  just  in 
course  of  painting,  and  made  a  gallant  though  hopeless  struggle 
to  bring  in  all  the  fresh  paint  as  fast  as  it  was  put  on  by  the 
painters!  Propolis  is  not  packed  in  cells,  but  is  used  as  soon 
as  brought  in,  the  trowel  mandibles  being  the  instruments 
used  in  putting  and  moulding  it  in  the  needed  place. 

Of  the  indoor  work  there  is  much  besides  those  industries 
already  referred  to,  namely,  wax-making,  comb-building,  honey- 
making,  crevice-chinking.  Because  the  queen  and  nurses 
(bees  less  than  two  weeks  old)  do  not  leave  the  hive,  their 
excreta  are  voided  within  doors;  there  are  also  bits  of  old, 
dirty  wax,  occasional  dead  bees,  and  various  other  waste 
substances  constantly  accumulating  in  the  hive.  Or,  rather, 
this  detritus  would  accumulate  if  the  workers  were  not  always 
keenly  careful  to  carry  out  all  such  stuff;  the  hive  is  constantly 
being  cleaned,  and  is  on  any  day  in  the  week  a  model  of  good 
housekeeping. 

Besides  keeping  the  hive  clean  the  workers  must  keep  it 
ventilated,  that  is,  clean  of  atmosphere  as  well  as  clean  of  floor 
and  wall.  This  is  done  by  setting  up  air-currents  through  the 
hive  which  carry  out  constantly  the  vitiated  air  and  thus  com- 
pel fresh  air  to  enter.  Always  near  the  exit  and  scattered 
through  the  hive,  especially  along  its  floor,  may  be  seen  bees 
standing  with  head  down  and  body  diagonally  up  and  wings 
steadily  vibrating  with  great  rapidity.  These  are  the  ven- 
tilating agents,  and  they  have  an  exhausting  and  tedious 
work. 

About  the  entrance  may  be  also  always  seen  bees  which  seem 
neither  to  be  leaving  the  hive  nor  entering  it,  but  which  move 
about  constantly  and  meet  and  touch  antennae  with  all  in- 
comers. These  are  the  warders  of  the  gate.  There  are  never 
wanting  enemies  of  the  industrious,  well-stocked  honey-bee 


WASPS,  ANTS  AND  BEES  195 

community,  whose  entrance  into  the  hive  must  be  vigorously 
guarded  against.  Yellow-jackets  hover  tentatively  around 
the  opening;  they  are  arrant  robbers  and  are  ready  to  take 
any  chance  to  get  at  the  full  honey-cells.  But  more  dangerous, 
because  of  the  habit  of  attacking  en  masse,  are  honey-bees  of 
other  hives.  Not  infrequently  a  desperate  foray  by  hundreds 


FIG.  91. — A  small  observation  hive  in  which  the  honey-comb  has  been 
destroyed  by  larvas  of  the  bee  moth,  Galleria  mellonella.  (Greatly  re- 
duced.) 

of  other  bees  will  be  made  into  a  hive,  especially  a  weak  one, 
and  a  pitched  battle  will  occur  in  and  about  the  entrance  and 
inside  the  hive  itself,  resulting  in  the  death  of  hundreds,  even 
thousands  of  bees.  More  insidious  and  even  more  dangerous 
are  the  stealthy  invasions  of  a  small  dusty-winged  moth,  the 
"large"  bee-moth,  Galleria  mellonella,  or  the  "small"  bee-moth, 


196    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Achroia  grisella,  which,  slipping  in  at  night  unobserved,  lay 
their  eggs  in  cracks;  the  larvae  which  hatch  from  the  eggs  feed 
on  the  wax  of  the  combs,  and  as  they  spin  a  silken  net  over 
them  wherever  they  go,  the  presence  of  many  such  larvae  works 
great  injury  both  in  the  actual  destruction  of  comb  and  in  the 
felting  and  cobwebbing  of  the  interior  of  the  hive  with  the 
tough  silken  netting.  Other  still  more  insidious  enemies  there 
are,  as  the  minute  bee-lice,  Braula,  which  attach  themselves 
to  the  bees  and  suck  out  their  body  juices,  and  the  invisible 
bacterial  germs  of  foul-brood  and  other  characteristic  bee 
diseases.  But  all  these  are  beyond  the  sensitiveness  of  the 
guards  to  recognize,  and  for  the  successful  fighting  of  them 
the  aid  of  the  bee-keeper  is  necessary. 

The  feeding  and  care  of  the  young  bees,  the  larvae,  have 
already  been  partly  described  in  the  account  of  the  life  history 
of  the  different  kinds  of  individuals  in  the  community,  and 
cannot  be  further  referred  to  in  this  brief  history  of  the  honey- 
bees' domestic  economy.  Of  course  only  the  more  conspicuous 
features  in  this  economy  have  been  described  at  all;  a  host  of 
interesting  details  cannot  even  be  mentioned.  But  enough 
has  been  said,  surely,  to  indicate  the  fascinating  field  of  obser- 
vation afforded  by  a  honey-bee  community.  If  such  a  com- 
munity be  kept  in  an  observation-hive  and  this  hive  be  placed 
conveniently  near  the  house,  or,  better,  inside  one's  room,  it 
will  prove  a  never-failing  source  of  interest  and  pleasure. 

Perhaps  it  had  better  be  explained  how  an  observation-hive 
can  be  kept  in  one's  room  without  interfering  with  coincident 
human  occupancy.  The  observation-hive,  in  the  first  place, 
may  be  simply  an  outdoor  hive  into  each  side  of  which  a 
large  pane  of  glass  has  been  let,  with  swinging  outer  wooden 
doors,  one  on  each  side,  which,  when  shut,  keep  the  hive  in 
normal  darkness,  but  opened,  allow  "observing"  to  go  on. 
In  addition  to  the  side  glasses  a  loose  sheet  of  glass  is  inserted 
just  under  the  ordinary  "honey-board"  or  removable  top  of 
the  hive.  Or  the  observation-hive  may  be  a  special  narrow, 
two-frame  hive,  with  both  sides  wholly  composed  of  glass  held 
in  the  narrow  wooden  frame  which  forms  the  ends  and  the  top 
and  bottom  of  the  hive.  A  black  cloth  jacket  should  be  kept 


WASPS,  ANTS  AND  BEES 


197 


on  the  hive  when  "observing"  is  not  going  on.  In  such  a 
hive,  which  will  obviously  hold  but  a  small  community  (one  of 
not  over  10,000  individuals)  any  single  bee  can  be  kept  con- 
tinuously under  observation,  as  there  are  no  side-by-side  frames 
between  which  it  can  crawl  and  thus  be  hidden  from  view. 
To  keep  either  of  such  hives  in  the  house  it  is  only  necessary 
to  substitute  for  a  pane  of  glass  in  a  window  a  thin  wooden 
pane  in  which  is  cut  a  narrow  horizontal  opening,  the  size  of 
the  regular  hive-opening  (if  the  latter  is  too  broad  it  can  be 


FIG.  92. — An  ordinary  bee-hive  made  into  an  observation  hive  by 
inserting  glass  panes  in  sides  and  putting  a  glass  sheet  under  the  wooden 
cover. 

closed  for  a  few  inches  at  each  end).  Or  a  narrow  broad  strip 
of  the  full  width  of  the  window  can  be  inserted  so  that  the 
lower  sash  of  the  window,  when  closed,  will  rest  upon  this 
strip.  In  the  strip  cut  a  narrow  opening  of  the  width,  or  less, 
of  the  hive  opening.  Set  the  observation-hive  on  a  table  or 
shelf  against  the  window  so  that  the  hive-opening  corresponds 
with  that  in  the  window  pane  or  window-strip.  Or,  better, 
place  it  six  or  seven  inches  from  the  window  and  connect  hive 
and  window-opening  by  a  shallow  broad  tunnel  of  wooden 


i98    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

bottom  and  sides  but  glass  top.  Over  the  glass  top  of  this 
tunnel  lay  a  sheet  of  black  cardboard,  which  will  keep  the 
tunnel  dark  normally,  but  which  can  be  simply  lifted  off 
whenever  it  is  desired  to  see  what  is  going  on  at  the  entrance. 
Here  can  be  seen  the  departure  of  the  foragers  and  their  arrival 
with  pollen,  propolis,  or  honey,  the  alertness  of  the  guards, 
the  repelling  of  robbers  and  enemies,  the  killing  of  drones,  the 
ventilating  etc.,  etc.  Through  the  glass  sides  of  the  hive 
itself  can  be  seen  all  the  varied  indoor  businesses  in  their  very 
undertaking;  the  life  history  of  each  kind  of  individual  can 
be  followed  in  detail;  the  wax-making  and  comb-building,  the 
storing  of  the  food-cells,  the  feeding  of  the  young  by  the  nurses, 
the  excitements,  the  joys,  and  the  discouragements,  the  whole 
course  of  life  in  this  microcosm. 

Practical  bee-keeping  is  based  first  of  all  on  a  sound  knowl- 
edge of  the  natural  history  of  the  honey-bee,  and  second  on  an 
acquaintance  with  the  methods  and  tools  used  in  handling 
hives  and  honey.  To  the  acquirement  of  the  first  of  these 
requirements  we  have  just  tried  to  guide  the  student.  For 
the  second  we  must  refer  him  to  some  one  of  the  many  book 
guides  for  such  work.  Anna  B.  Comstock's  "How  to  Keep 
Bees"  is  a  good  small  book;  Root's  "A,  B,  C  and  X,  Y,  Z  of 
Bee  Culture"  is  a  good  larger  one. 

Cross-pollination  of  Flowers  by  Bees  and  Other  Insects. — A 
means  by  which  insects  indirectly  render  a  great  economic 
service  to  man  is  by  their  cross-pollination  of  flowers.  The 
nectar  of  flowers  is  a  favorite  food  with  many  insects;  all  the 
moths  and  butterflies,  all  the  bees  and  many  kinds  of  flies  are 
nectar-drinkers.  Flower-pollen,  too,  is  food  for  other  hosts 
of  insects,  as  well  as  for  many  of  those  which  take  nectar. 
The  hundreds  of  bee  kinds  are  the  most  familiar  and  con- 
spicuous of  the  pollen-eaters,  but  many  little  beetles  and  some 
other  obscure  small  insects  feed  largely  on  the  rich  pollen- 
grains.  But  the  flowers  do  not  provide  nectar  and  pollen  to 
these  hosts  of  insect  guests  without  demanding  and  receiving 
a  payment  which  fully  requites  their  apparent  hospitality. 
This  payment  is  the  cross-pollination  by  the  insects  of  the 
nectar-providing  flowers.  The  agency  of  insects  in  this  matter 


WASPS,  ANTS  AND  BEES  199 

has  long  been  recognized,  and  some  orchard  growers  keep 
hives  of  bees  in  or  near  their  orchards  to  ensure  the  advantage 
of  cross-pollination  to  their  trees. 

Cross-pollination  is  simply  the  bringing  of  pollen  from  one 
plant  individual  to  the  flowers  of  another  individual  of  the  same 
species.  Self-pollination  is  the  getting  of  pollen  from  the 
stamens  of  one  flower  on  to  the  stigma  of  the  same  flower. 
The  advantage  of  cross-pollination,  as  first  experimentally 
proved  by  Darwin,  and  since  then  confirmed  by  other  experi- 
menters and,  without  scientific  intention  but  none  the  less 
effectively,  by  hosts  of  economic  plant-breeders  (horticul- 
turists, florists,  etc.),  lies  in  the  fact  that  the  seeds  produced 
when  the  ovules  of  one  plant  are  fertilized  by  the  sperm-cells 
(in  the  pollen)  of  another,  develop  plant  individuals  of  mark- 
edly stronger  growth  (shown  in  size  of  plant  and  its  fruits,  in 
number  of  seeds,  etc.),  than  seeds  produced  by  the  fertilization 
of  ovules  by  sperm-cells  of  the  same  plant.  For  the  sake  of 
insuring  this  cross-pollination  the  flowers  of  many  plants  are 
highly  specialized.  This  specialization  follows  two  general 
lines:  One  includes  means  of  preventing  self-pollination  such 
as  having  stamens  and  pistils  ripen  at  different  times,  or  be  of 
such  different  lengths  that  the  pollen  cannot  fall  on  the  pistils 
in  the  same  flower,  etc.  The  other  line  includes  means  for 
attracting  insects,  such  as  color  and  pattern  and  the  secretion 
of  nectar,  and  means,  such  as  shape,  curious  modification  of 
flower  parts,  etc.,  to  compel  the  visiting  insects  both  to  leave 
on  the  stigma  pollen  brought  from  other  flowers  and  to  carry 
away  from  the  anthers  pollen  from  the  flower  being  visited. 
Honey  bees  are  undoubtedly  the  most  important  of  all  insects 
concerned  with  cross-pollination,  and  perform  in  this  way  a 
great  service  to  flower  and  orchard  growers. 

The  Ants. — The  ants  constitute  the  fifth  and  last  principal 
group  of  Hymenoptera,  and  for  their  adequate  treatment  a 
book  much  larger  than  the  whole  of  this  one  would  be  necessary. 
Such  a  book,  indeed,  has  been  recently  written  by  Professor 
W.  M.  Wheeler,1  the  foremost  American  student  of  ants,  and 

1  Wheeler,  W.  M.  Ants,  their  Structure,  Development  and  Behavior, 
1910. 


200    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

it  is  one  of  the  most  fascinating  and  stimulating  books  of 
natural  history  ever  written. 

About  five  thousand  kinds  of  ants  are  known,  all  of  which 
live  socially  in  small  or  large  communities  comprising  three 
usually  well-distinguished  types  of  individuals,  namely,  fertile 
females,  or  queens,  males,  or  drones,  and  sterile  females,  or 
workers.  The  workers  are  wingless,  while  the  males  and  queens 
are  winged,  although  the  queens  pull  off  their  wings  after 
mating.  There  may  be  a  certain  further  amount  of  structural 
differentiation  within  a  species  in  that  the  workers  may  be  of 
two  or  three  different  types.  The  general  appearance  of  ants 
is  so  characteristic  that  they  are  readily  distinguished  from  all 
other  insects,  and  their  extraordinarily  developed  communal 
life  is  more  or  less  familiarly  known  to  every  observer  or  reader. 
To  the  economic  zoologist,  however,  ants  do  not  present  any 
very  large  importance.  A  few  kinds  of  house  ants  can  be 
extremely  troublesome  and  a  few  garden-infesting  kinds  do 
some  injury  to  vegetables  and  fruits.  Their  greatest  damage 
probably  is  done  indirectly,  through  their  habits  of  protecting 
and  caring  for  plant-lice  (aphids),  from  which  they  obtain 
their  favorite  food  of  "honey-dew."  All  of  these  protected 
aphids  are  injurious  to  plants  because  they  suck  their  sap. 

The  ant  communities  live  in  nests  comprising  a  number  of 
irregular  chambers  and  galleries,  most  of  the  species  living 
underground,  although  a  considerable  part  of  the  nest  may  be 
above  the  normal  ground  surface,  built  up  as  a  mound  or  hill- 
side, of  more  or  less  symmetry  and  greater  or  less  size.  This 
part  above  ground  may  be  composed  chiefly  or  wholly  of  soil 
brought  up  from  below  surface,  or  may  be  partly  or  wholly 
made  up  of  bits  of  wood,  grass  and  weed  stems,  chaff  or  pine- 
needles.  The  nest  may  be  made  under  a  stone  or  log,  or  be 
established  in  a  wholly  exposed  place.  Most  ants  keep  their 
nest  fairly  near  the  surface,  but  a  few  mine  deeply.  Still  other 
species  tunnel  out  their  corridors  and  rooms  in  wood — an  old 
log  or  stump,  dry  branches,  or  what  not — while  yet  others  live 
in  the  stems  of  plants,  in  old  plant-galls,  in  hollow  thorns  and 
spines;  finally  a  few  make  nests  of  delicate  paper  or  tie  leaves 
together  with  silken  threads.  Very  wonderful  are  some  of  the 


WASPS,  ANTS  AND  BEES  201 

inter-relations  between  certain  plants  and  certain  ant  species 
in  tropic  regions,  whereby  the  plant  seems  to  have  developed 
suitable  cavities  for  the  accommodation  of  the  ants,  whose  pres- 
ence in  turn  is  advantageous  to  the  plant  by  the  protection  it 
affords  against  the  ravages  of  certain  leaf-eating  insects  which 
are  repelled,  or  rather  attacked  as  prey,  by  the  ants.  In  many 
cases  two  ant  species  will  live  together  in  a  compound  or  mixed 
nest,  the  relation  between  the  two  species  being  (a)  simply 
that  of  two  close  neighbors,  friendly  or  unfriendly;  (b)  that 
of  two  species  having  their  nests  with  "inosculating  galleries" 
and  "  their  households  strangely  intermingled  but  not  actually 
blended";  (c)  that  of  one  species,  usually  with  workers  of 
minute  size,  which  lives  in  or  near  the  nests  of  other  species 
and  preys  on  the  larvae  or  pupae  or  surreptitiously  consumes 
certain  substances  in  the  nests  of  their  hosts — some  different 
larger  species — that  is,  the  relation  of  thief  and  householder; 
(d)  that  of  two  species  living  in  one  nest  but  with  independent 
households,  one  of  these  species  living  as  a  guest  or  inquiline 
at  the  expense  of  the  food-stores  of  the  other,  but  consorting 
freely  with  their  hosts  and  living  with  them  on  terms  of  mutual 
toleration  or  even  friendship;  and  (e)  that  of  slave-maker  and 
slave,  a  relation  not  at  all  rare  and  readily  observed  all  over 
our  country. 

Inside  the  nest  the  eggs  are  laid  by  the  queen  or  queens  in 
large  numbers,  not  in  separate  cells  as  with  the  wasps  and 
bees,  but  in  little  piles  heaped  together  in  various  rooms  and 
sometimes  moved  about  by  the  workers.  The  hatching  larvae, 
tiny,  white,  footless,  helpless,  soft-bodied  grubs,  are  fed  by  the 
workers  either  a  predigested  food  regurgitated  from  the  mouth, 
or  chewed  fresh  insects,  caught  and  killed  by  the  workers,  or 
dry  seeds  or  other  vegetable  matter  brought  into  the  hive  and 
stored  in  the  "granary"  rooms.  A  single  species  may  use  all 
these  different  kinds  of  food,  but  for  the  most  part  the  ants 
belonging  to  one  species  habitually  use  one  kind  of  food  for  the 
young.  The  primitive  food  consists  of  seeds  and  cut-up 
insects.  The  adult  ants  feed  on  a  variety  of  substances,  both 
animal  and  vegetable,  almost  all,  however,  having  a  -special 
taste  for  sweetish  liquids,  such  as  the  secreted  honey- dew  of 


202    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

plant-lice,  scale-insects,  certain  small  beetles  and  others,  and 
the  sugary  sap  of  certain  trees.  The  males  and  fertile  females 
are  fed  by  the  workers. 

Besides  feeding  the  larvae,  the  nurses  have  to  see  that  the 
young  enjoy  suitable  temperature  and  humidity  of  the  atmos- 
phere; this  is  accomplished  by  moving  the  larvae  or  pupae  from 
room  to  room,  farther  below  the  surface,  or  even  out  into  the 
warm  sunshine  above  ground.  The  carrying  about  of  ants' 
"eggs,"  which  are  not  eggs  but  usually  the  cocooned  pupae, 
by  the  workers,  is  a  familiar  sight  around  any  ant-nest,  particu- 
larly a  disturbed  one.  The  various  special  industries  under- 
taken by  ants,  as  the  attendance  on  and  care  of  honey  dew- 
secreting  plant-lice,  the  fungus-growing  in  their  nests,  the 
harvesting  (but  not  planting!)  of  food-seeds,  the  waging  of 
wars  for  pillage  or  slave-making,  the  long  migrations,  etc.,  etc., 
are  more  or  less  familiar  through  much  true  and  some  inaccu- 
rate popular  writing. 

In  any  community  there  may  live  at  one  time  several  (two 
to  thirty)  queens  with  wings  removed.  In  small  colonies  there 
is,  however,  usually  but  one.  As  already  mentioned,  winged 
ants  are  to  be  seen  only  at  certain  times  in  the  year.  When  a 
brood  of  sexual  individuals  (males  and  females)  is  matured  in 
the  community,  these  winged  forms  issue  on  a  sudden  impulse 
(comparable  in  a  way  with  the  outwinging  ecstasy  of  bees  at 
swarming  time)  from  all  the  openings  of  the  nest  and  take  wing. 
The  air  may  be  swarming  with  them,  flights  from  neighboring 
nests  intermingling  and  joining.  This  is  the  mating  flight, 
and  after  it  is  over  those  ants  which  have  escaped  the  bird 
attacks  and  other  dangers  attending  this  bold  essay  into  the 
outer  world  alight  or  fall  exhausted  to  the  ground;  the  males 
soon  die,  while  the  females  pull  the  wings  from  the  body  and 
get  under  cover.  In  the  communal  nest,  therefore,  winged 
ants  are  rarely  found.  The  life  of  the  workers  of  most  ant 
species  is  conspicuously  longer  than  that  of  other  social  insect 
workers;  they  live  for  from  one  to  three  or  four  or  even  five 
years.  Lubbock  has  kept  workers  until  six  years  old,  and 
queens  until  seven.  The  males  all  die  young,  but  both  other 
kinds  of  individuals  are  exceptionally  long-lived  for  insects. 


WASPS,  ANTS  AND  BEES  203 

There  are  several  different  ways  in  which  a  new  community 
may  be  founded.  A  fertilized  queen  may  begin  alone  the 
establishment  of  a  new  community  by  building  a  little  nest, 
laying  a  few  eggs,  caring  for  the  hatching  larvae  herself,  and 
thus  raising  by  her  unaided  exertions  a  small  brood  of  neuter 
workers  which  are  always  normally  undersized,  probably  from 
insufficient  nourishment.  This  mode  of  community  founding 
is  just  like  that  obtaining  among  the  social  wasps  and  the 
bumble-bees.  An  interesting  fact  in  these  cases  is  that  the 
food  given  the  larvae  by  the  queen  is  supplied  from  her  own 
body,  by  regurgitation  through  the  mouth,  no  food  whatever 
being  brought  into  the  nest  from  the  time  that  the  queen  first 
begins  to  lay  eggs  until  this  first  brood  is  matured. 

Another  method  of  colony  founding  is  by  the  withdrawal  of 
young  fertilized  queens  each  with  a  group  of  workers  from  an 
old  and  over-populous  community.  Still  other  methods  are 
those,  recently  carefully  worked  out  by  Wheeler  and  other 
students,  in  which  queen  ants  of  one  species  found  colonies  by 
the  aid  of  workers  of  other  species.  Several  phases  of  this 
method  have  been  observed.  In  one  phase  a  queen  enters  a 
colony  of  an  alien  species  and  decapitates  its  queen  or  is  the 
occasion  of  her  being  killed  off  by  her  own  workers.  The 
intruding  queen  is  then  adopted  by  the  workers  and  proceeds 
to  lay  eggs  whose  hatching  larvae  are  reared  by  the  alien 
workers  and  a  compound  or  mixed  colony  is  thus  formed.  In 
another  phase  of  this  general  method  a  queen  enters  a  colony 
of  another  species,  snatches  up  the  worker  brood  and  kills  any 
of  the  workers  or  queens  that  endeavor  to  dispute  her  posses- 
sions. The  ants  hatch  with  a  sense  of  affiliation  with  their 
foster  mother  and  proceed  to  rear  her  eggs  and  larvae  as  soon 
as  they  appear.  Here,  too,  the  colony  is  formed  by  a  mixture 
of  two  species,  but  the  workers  produced  by  the  intrusive 
queens  inherit  her  predatory  instincts  and  therefore  become 
slave-makers.  They  keep  on  kidnapping  worker  larvae  and 
pupae  from  the  nests  of  the  alien  species,  carry  them  home,  and 
eat  some  of  them  but  permit  many  to  mature,  so  that  the  mixed 
character  of  the  colony  is  maintained. 

The  observation  and  study  of  ants'  ways  must  be  mostly 


204    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

done  in  the  field,  but  some  species  readily  live  in  artificial  nests 
prepared  for  them  indoors.  These  nests  can  be  so  arranged 
that  much  of  the  home  life  of  the  ants  can  be  observed. 

A  simple  formicarium,  or  ant  nest,  may  be  made  by  mounting 
an  inverted  bell  glass  on  a  wooden  block  which  is  set  like  an 
island  in  a  shallow  pan  of  water.  Enough  of  the  contents 
(soil  and  ants)  of  a  nest  should  be  brought  in  and  transferred 
to  the  bell  glass  to  fill  it  about  half  full.  A  cover  of  dark  paper 
or  cloth  should  be  placed  around  the  bell  glass  as  high  as  the  soil 
fills  it,  in  such  a  manner  that  it  may  be  readily  removed  at 
times  of  observation.  The  ants  in  their  nest  building  will 
make  some  of  their  run  ways  and  chambers  next  to  the  dark- 
ened glass,  and,  by  removing  the  cloth,  may  be  seen  at  work. 

Janet,  a  distinguished  French  student  of  ant  life,  uses  a 
block  of  porous  earthenware  in  which  several  little  chambers 
or  hollows  have  been  made,  connecting  with  each  other  by 
little  surface  grooves,  the  whole  covered  with  a  glass  plate, 
and  over  that  an  opaque  cover.  Into  a  cavity  at  one  end  of 
the  block  he  puts  water  which  soaks  some  distance  along  the 
length  of  the  block,  thus  rendering  some  chambers  humid, 
while  others  at  the  far  end  are  dry.  He  gives  the  ants  no  soil, 
forcing  them  to  use  the  already  made  chambers.  This  formi- 
carium reveals,  therefore,  none  of  the  secrets  of  nest-building, 
but  it  does  reveal  admirably  a  host  of  those  interesting  pro- 
cesses connected  particularly  with  the  life  history  of  the  individ- 
uals of  the  colony. 

Miss  Adele  Field,  an  American  student  of  ants,  has  devised 
a  nest  (Fig.  93)  in  which  glass  is  used  for  the  base,  outer  wall 
and  partitions.  A  bit  of  sponge,  kept  moist,  is  placed  in  one  of 
the  rooms.  The  glass  base  is  double  thick  and  placed  on  thick 
white  blotting  paper  for  background,  and  the  walls  and  parti- 
tions are  narrow  strips  of  glass  glued  to  the  base  with  crockery 
cement.  On  walls  and  partitions  are  glued  strips  of  Turkish 
toweling.  On  this  is  laid  a  thin  glass  roof  frame  for  each  room. 
An  outer  removable  roofing  of  blotting  paper  makes  all  the 
interior  of  the  nest  dark,  except  the  food  room  which  should 
not  be  covered  as  it  represents  the  ants'  outer  world. 

Sponge  cake,  apple,  mashed  walnut  and  the  muscular  parts 


WASPS,  ANTS  AND  BEES 


205 


of  larvae  of  insects  are  among  the  ants'  most  liked  edibles,  says 
Miss  Field. 

The  extremely  highly  developed  instincts  of  the  social 
Hymenoptera  (social  wasps,  social  bees  and  ants)  have  led  to 
their  being  called  the  most  intelligent  of  insects.  But  as  far  as 
our  present  knowledge  goes  we  are  not  justified  in  attributing 
any  intelligence,  in  the  strict  meaning  of  the  term,  to  any 
insects.  Their  behavior  is  practically  wholly  controlled  by 
inherited  instincts,  which  fit  them  to  go  through  a  certain  life 


FIG.  93. — Plan  of  the  Fielde  ant-nest,  ten  inches  by  six  inches,  a,  En- 
trance and  exit  to  food-rooms  d);  2,  nursery;  3,  sponge-room;  b,  screens; 
m,  passage. 

routine  very  effectively,  but  which  leave  them  helpless  if  by 
any  chance  they  are  submitted  to  wholly  new  conditions. 
Much  experimental  work  has  been  done  with  the  wasps,  bees 
and  ants,  to  test  their  capacities  for  successful  modifications  of 
their  behavior,  and  the  weight  of  authority  is  against  admitting 
their  possession  of  real  reason  or  intelligence.  In  this  connec- 
tion the  books  of  Fabre,  the  French  "Homer  of  insect  life," 
those  of  the  Peckhams,  American  students  of  solitary  and 
social  wasps,  and  of  Wheeler,  the  American  student  of  ants, 
should  be  read  by  students.  They  contain  the  most  fascinat- 
ing stories  of  insect  life  which  can  be  written. 


CHAPTER  XIX 
SCORPIONS,  SPIDERS,  MITES  AND  TICKS 

The  scorpions,  spiders,  mites  and  ticks,  composing  the  class 
Arachnida  of  the  branch  Arthropoda,  are  popularly  regarded  as 
insects  but  they  differ  from  the  insects  in  several  important 
respects.  They  have  four  pairs  of  legs  instead  of  three  pairs, 
the  body  is  not  divided  into  three  well  defined  regions,  as  it  is 
in  most  insects,  but  into  two,  and  they  have  no  antennae. 
There  are  also  important  differences  in  the  respiratory  system 
and  other  internal  structures. 

The  class  is  a  large  one  including  many  diverse  forms. 

Scorpions. — The  scorpions,  order  Arthrogastra,  are  found 
chiefly  in  warm  regions.  They  are  usually  nocturnal,  hiding 
away  under  stones  or  in  crevices  during  the  day,  and  coming 
forth  at  night  to  capture  their  prey,  which  consists  chiefly  of 
insects  and  spiders.  These  they  seize  and  hold  with  their  large 
pincer-like  maxillary  palpi  and  sting  with  the  poison  fang  at  the 
end  of  the  long  narrow  part  of  the  abdomen.  The  first  seven 
segments  of  the  abdomen  are  broad  and  flattened,  but  the  last 
five  segments  are  narrowed,  more  rounded  and  whip-like.  The 
last  segment  bears  the  poison-fang  or  sting,  the  poison  from 
which  is  quickly  fatal  to  most  small  animals.  Some  species 
are  quite  poisonous  to  man,  but  the  kinds  found  in  the  United 
States,  while  they  may  inflict  a  painful  sting,  are  not  usually 
dangerous. 

Spiders. — In  the  spiders,  order  Araneina,  the  abdomen  and 
the  cephalothorax  are  very  distinctly  separated  but  the  seg- 
ments of  each  region  are  so  closely  fused  as  to  be  indistinguish- 
able. The  four  pairs  of  legs  vary  in  length  according  to  the 
habits  of  the  different  species;  some  are  fitted  for  running, 
others  for  jumping,  others  for  walking  over  the  ground  or 
grass  or  pver  delicately  spun  webs.  The  pedipalpi,  or  feet- 

206 


207 

like  palpi,  are  sometimes  one-fourth  to  one-half  as  long  as  the 
legs.  The  mandibles,  or  chelae,  are  large  and  terminate  in  a 
slender  sharp-pointed  fang,  through  which  poison  flows  when 
a  spider  bites  its  prey.  The  bite  usually  quickly  kills  insects 
and  other  small  animals  but  as  a  rule  does  not  seriously  affect 
man.  A  few  species,  however,  are  very  venomous,  and  a  bite 
from  one  of  them  may  result  in  great  suffering,  rarely  in 


FIG.  94. — Web  of  an  orb- weaver,  Zilla  calif ornica;  the  viscid  threads  are 
omitted  from  part  of  the  web;  a  trap-line  runs  from  the  center  to  a  retreat 
at  one  side.  (Much  reduced.) 

death.  The  effect  of  a  spider's  bite  does  not  depend  altogether 
upon  the  kind  of  spider,  the  condition  of  the  victim's  blood 
being  a  considerable  factor.  Two  people  may  be  bitten  by  the 
same  kind  of  spider  and  one  suffer  little  while  the  effect  on  the 
other  may  be  very  serious.  The  most  common  of  the  very 
poisonous  spiders,  and  the  only  one  to  be  much  feared  in  this 
country,  is  the  "hour-glass"  spider,  or  "black  widow" 
Latrodectes  mactans.  This  is  a  small-sized  sooty  black 


2o8    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

spider,  the  female  of  which  has  a  round  abdomen  that  is 
marked  on  the  underside  by  a  bright  red  spot,  usually  hour- 
glass shaped.  The  slender  abdomen  of  the  male  has  three 
light  spots  or  dashes  along  the  median  line  and  three  or  four 
lateral  stripes.  The  very  young  of  both  sexes  have  little 
black  on  them  and  immature  females  are  colored  much  like 
the  males.  This  species  is  cosmopolitan.  In  the  United  States 
it  occurs  as  far  north  as  Massachusetts  but  is  more  common  in 
southern  regions.  These  spiders  are  found  in  the  fields  on 
plants  or  among  loose  stones  and  around  houses  in  dark 
corners  or  in  boxes  or  rubbish. 

The  webs  that  spiders  spin  for  traps  to  ensnare  their  prey  or 
to  line  their  nests  or  to  protect  their  eggs  are  made  of  silken 
threads  of  various  sizes.  Some  of  these  threads  are  composed 
of  several  finer  threads  united.  Spiders  produce  several  kinds 
of  silk,  one  kind  being  always  viscid  and  sticky.  Most 
spiders  have  three  pairs  of  spinnerets,  a  few  having  but  two 
pairs,  situated  at  the  tip  of  the  abdomen.  On  the  ends  of 
these  short  finger-like  spinnerets  are  many  minute  openings 
through  which  the  fine  silken  threads  are  drawn.  These 
openings  lie  in  little  papillae,  called  spinning  spools  and 
spigots.  When  the  tips  of  the  spinnerets  are  placed  close 
together,  the  issuing  threads  all  unite  into  a  large  strong 
thread.  If  the  spinnerets  are  held  further  apart  the  broad 
silken  bands  are  produced. 

The  great  hairy  tarantulas  of  our  southern  and  western  states 
line  their  burrows  with  a  thin  layer  of  silk.  The  trap-door 
spiders  usually  make  a  heavier  lining  sometimes  dense  and 
tough,  but  with  a  smooth  soft  silken  surface.  The  door  that 
these  spiders  make  to  guard  the  entrance  to  their  burrow  is 
made  of  silk  and  earth,  leaves,  grass  or  moss,  always  resembling 
closely  the  ground  or  ground-covering  around  it.  The  com- 
mon black  running  spiders  that  often  carry  their  egg  sacs  with 
them  and  the  stout-bodied  little  jumping  spiders  which  leap 
on  their  prey,  spin  but  little  web. 

The  sedentary  spiders,  or  those  which  spin  webs  of  various 
sorts  to  capture  their  prey,  include  most  of  the  common  kinds. 
The  cob- web  weavers,  which  are  one  of  the  trials  of  the  house- 


SCORPIONS,  SPIDERS,  MITES  AND  TICKS     209 

keeper,  the  funnel-web  weavers  found  in  the  woods  and 
meadows,  and  the  various  orb- weavers  are  all  most  interesting 
and  deserve  more  notice,  but  as  they  are  of  no  particular 
economic  importance  except  as  they  destroy  noxious  insects, 
they  will  not  be  discussed  further  here.  The  best  book  about 
American  spiders  is  "The  Spider  Book"  by  Professor  J.  H. 
Comstock. 


FIG.  95. — Web  of  a  grass  spider,  Agalena  sp.     (Reduced.) 

TICKS  AND  MITES  (ORDER  ACARINA) 

From  an  economic  standpoint  the  mites  and  ticks,  consti- 
tuting the  order  Acarina,  are  by  far  the  most  important  mem- 
bers of  this  class.  The  body  is  very  compact,  the  cephalo- 
thorax  and  abdomen  being  closely  fused.  This  character 
will  serve  to  separate  them  from  the  spiders,  the  young  of 
which  might  be  mistaken  for  mites. 

Ticks. — The  ticks  are  all  comparatively  large,  that  is,  they 

are  large  enough  to  be  seen  with  the  unaided  eye,  even  in  their 

younger  stages,  and  some  grow  to  be  half  an  inch  long.     The 

young  when  first  hatched  have  only  six  legs  but  after  the  first 

14 


210    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


moult  another  pair  appears.  The  sucking  beak,  which  is 
thrust  into  the  host  when  the  tick  is  feeding,  is  furnished  with 
many  strong,  recurved  teeth  which  hold  so  firmly  that  the 
head  is  often  torn  from  the  body  and  left  in  the  skin  of  the  host 
when  the  tick  is  forcibly  removed. 

Ticks  are  wholly  parasitic  in  their  habits.  Some  of  them 
live  on  their  host  practically  all  their  lives,  only  dropping 
to  the  ground  when  fully  mature  to  deposit  their  eggs.  Others 


FIG.  96. — Castor  bean  tick,  Ixodes  ricinus,  not  fully  gorged.     (Magnified 
about  five  times.) 

leave  their  host  twice  to  molt  in  or  on  the  ground.  The 
female  lays  her  eggs,  1000  to  10,000  of  them,  on  or  beneath 
leaves  and  other  litter  on  the  ground.  The  young  "seed- 
ticks"  that  hatch  from  these  in  a  few  days,  soon  crawl  up  on 
some  nearby  blades  of  grass  or  on  a  bush  or  shrub  and 
wait  quietly  and  patiently  until  some  animal  comes  along. 
If  the  animal  comes  close  enough  the  ticks  leave  the 
grass  or  other  support  and  cling  to  their  new  found 
host  and  are  soon  taking  their  first  meal.  Of  course 
thousands  of  them  are  disappointed  and  starve  before  their 


SCORPIONS,  SPIDERS,  MITES  AND  TICKS     211 


host  appears,  but  as  they  are  able  to  live  for  a  remarkably  long 
time  without  taking  food  their  patience  is  often  rewarded  and 
the  long  fast  ended.  Those  species  which  drop  to  the  ground 
to  molt  must  again  climb  to  some  favorable  point  and  wait 
for  another  host  on  which  they  may  feed  for  awhile.  Then 
they  drop  to  the  ground  for  a  second  molt  and  if  they  are 
successful  in  gaining  a  new  host  for  the  third  time  they  feed  and 
develop  until  fully  mature  and  the  female  is  ready  to  lay  her  eggs. 


FIG.  97. — Amblyomma  variegatum;  several  ticks  belonging  to  the  genus 
Amblyomma  transmit  various  diseases  of  domestic  animals.  (Magnified 
about  six  times.) 

The  presence  of  even  a  few  ticks  on  an  animal  is  always  a 
source  of  annoyance  and  they  often  occur  in  such  numbers  as 
to  affect  seriously  some  of  our  domestic  animals.  Chickens, 
dogs,  horses  and  cattle,  all  have  their  particular  kinds  of  ticks, 
some  of  which  commonly  attack  man  when  the  opportunity 
offers.  The  bites  of  ticks  often  cause  great  pain.  Sickness 
and  death  sometimes  follows  the  bite  of  some  certain  species, 
but  this  probably  only  under  exceptional  conditions  or  when  the 


212     ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

tick  carries  the  parasite  of  some  disease.  Their  chief  impor- 
tance, indeed,  lies  in  the  fact  that  they  are  concerned  in  the 
transmission  of  several  diseases  that  are  caused  by  Protozoan 
parasites.  The  Texas  fever  of  cattle  and  the  spotted  or  Rocky 
Mountain  fever  of  man  are  the  most  important  of  such  diseases 
in  America.  These  will  be  discussed  in  Chapter  XXVIII. 

The  chicken-tick,  Argas  persicus,  is  a  very  serious  pest  in 
the  southern  states.  It  has  a  world-wide  distribution,  and  in 
Persia,  where  it  has  habits  similar  to  the  bed-bug,  it  is  one  of 
the  most  dreaded  pests,  sometimes  becoming  so  numerous 
that  the  inhabitants  desert  the  town  rather  than  try  to  rid  it 
of  the  pests. 

In  Africa  the  most  common  tick,  Ornithodorus  moubata,  lives 
in  the  huts  of  the  natives  and  has  habits  similar  to  the  bed-bug. 
Besides  being  a  source  of  great  annoyance  it  transmits  a 
disease  known  as  relapsing  fever  which  has  at  different  times 
been  introduced  into  the  United  States,  but  has  not  become 
established  here. 

Mites. — The  mites  are  much  smaller  than  the  ticks,  so  small 
that  they  are  not  ordinarily  seen  unless  one  is  searching  for 
them.  Yet  many  of  them  make  their  presence  destructively 
or  painfully  evident,  for  they  are  not  only  important  pests 
of  cultivated  plants,  but  they  attack  man  and  domestic 
animals. 

Perhaps  the  best  known  of  the  mites  is  the  "red  spider" 
of  the  greenhouses,  Tetranychus  bimaculatus,  which  is  one  of 
the  worst  pests  that  occurs  in  such  places.  It  is  found  out  of 
doors  also  and  in  some  regions  may  totally  defoliate  almond 
and  prune  trees  and  berry  bushes  and  seriously  injure  many 
other  plants.  These  mites  do  not  always  have  the  character- 
istic red  color  but  during  the  time  that  they  are  feeding  they 
may  be  light  or  dark  green  with  dark  colored  spots.  This 
species  passes  the  winter  in  the  ground.  The  usual  method  of 
control  is  to  dust  the  trees  thoroughly  with  fine  dry  sulphur,  or 
the  sulphur  may  be  mixed  with  water,  i  Ib.  to  5  gallons  of 
water,  and  applied  as  a  spray.  The  fumes  from  the  sulphur 
kill  the  mites. 

Another  mite,  Bryobia  pratensis,  also  commonly  called  "red 


SCORPIONS,  SPIDERS,  MITES  AND  TICKS     213 

spider, "  often  does  much  damage  to  fruit  trees,  particularly 
on  the  Pacific  Coast.  The  eggs  are  laid  on  the  branches  of 
the  tree,  where  they  remain  over  winter,  the  young  mites 
issuing  about  the  time  the  leaf  buds  open.  They  may  be 
controlled  by  spraying  the  eggs  with  the  lime-sulphur  wash 
(see  page  415)  just  before  the  eggs  hatch  in  the  spring,  or  by 
spraying  or  dusting  with  sulphur.  This  same  species  is  often 
an  important  pest  on  clover  and  grasses  and  is  then  known  as 
the  clover-mite.  In  the  Mississippi  Valley  states  they  some- 
times swarm  into  dwelling  houses  late  in  the  fall.  Dry  sulphur 
dusted  around  the  windows  and  doors  or  other  places  where  the 
mites  enter  the  house,  or  the  free  use  of  pyrethrum  after  they 
have  gained  an  entrance,  will  give  relief. 

Two  other  red  spiders,  Tetranychus  mytilaspidis,  and 
T.  sexmaculatus,  are  serious  pests  of  citrus  trees.  They  are 
controlled  by  dusting  the  trees  thoroughly  with  finely  powdered 
sulphur. 

The  blister-mites,  Eriophyes,  are  minute  whitish,  grub-like 
creatures  that  bore  into  the  tissue  of  the  leaves  of  many  plants. 
The  pear-leaf  blister-mite  is  perhaps  the  most  important  of 
these.  They  spend  the  winter  in  the  buds  and  as  the  leaves  be- 
gin to  develop  they  make  their  way  into  the  tissue,  causing 
green  or  reddish  blisters.  They  may  be  controlled  by  spray- 
ing during  the  late  fall  or  early  spring  with  kerosene  emul- 
sion diluted  with  five  parts  of  water,  or  with  the  lime-sulphur 
wash. 

Of  the  mites  that  attack  man,  the  young  harvest-mites,  or 
"jiggers",  are  probably  the  most  familiar.  Normally  these 
little  mites  live  on  plants,  but  when  opportunity  offers  they  will 
crawl  on  man  or  any  other  animal  and  burrow  into  the  skin, 
causing  intolerable  itching.  Where  these  mites  are  trouble- 
some, one  should  avoid  sitting  or  lying  on  the  grass  or  in 
other  places  where  they  may  occur.  Harvest  men  and  others 
whose  work  exposes  them  to  these  pests  may  get  some  relief 
by  dusting  sulphur  in  the  underclothing  and  shoes,  and 
by  bathing,  using  a  strong  carbolic  or  tar  soap,  as  soon  as  they 
return  from  the  fields.  Sulphur  ointments  are  also  used. 

The  minute,  almost  round,  whitish  mites,  Sarcoptes  scabiei, 


2i4    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


that  cause  the  disgusting  disease  known  as  itch  are  seldom 
found  except  on  unclean  people.  These  mites  live  normally 
in  the  skin,  often  burrowing  deep  and  causing  intense  itching. 
Sulphur  ointments  and  other  washes  are  used  as  remedies, 
but  on  account  of  their  burrowing  habits  these  mites  are  hard 
to  kill.  Cleanliness  will  prevent  infection. 

Closely  related  to  the  itch-mite  of  man  are  several  kinds 
attacking  domestic  animals,  causing  mange,  scab,  etc.  The 
variety  infesting  horses  burrows  in 
the  skin  and  produces  sores  and 
scabs,  and  is  a  source  of  very  great 
annoyance.  These  mites  may  also 
migrate  to  man.  Tobacco  water 
and  sulphur  ointments  are  used  as 
remedies. 

Horses  and  cattle  and  other  do- 
mestic animals  are  also  infested  by 
mites  of  the  species  Psoroptes  com- 
munis,  which  cause  the  common 
mange.  These  do  not  burrow  into 
the  skin,  but  live  on  its  surface  in 
colonies,  feeding  on  the  skin  and 
causing  crusts  or  scabs.  The  in- 
flammation causes  the  animal  to 
scratch  and  rub  constantly,  and 

often  results  in  the  loss  of  much  of  the  hair.  Single  animals 
may  be  treated  with  sulphur  ointments  or  with  lime-sulphur 
mixtures;  where  several  are  to  be  treated,  dipping  vats  should 
be  used. 

The  mites,  Psoroptes  co'mmunis  var.  ovis,  that  cause  scab  in 
sheep,  are  among  the  worst  pests  that  sheep  owners  have  to 
contend  with.  Once  introduced  into  the  herd  they  spread 
rapidly  so  that  the  whole  flock  may  soon  become  infested.  The 
fleece  of  scabby  sheep  becomes  rough  and  felted  and  is  easily 
rubbed  or  pulled  off,  often  leaving  the  sheep  very  ragged  and 
sore.  The  most  satisfactory  treatment  for  scabby  sheep  is  to 
hand  dip  them  or  drive  them  through  vats  containing  lime  and 
sulphur  or  tobacco  mixtures. 


FIG.  98. — Itch-mite,  Sar- 
coptes  scabiei,  female,  dor- 
sal aspect.  (Greatly  mag- 
nified; after  Fiirstenberg.) 


SCORPIONS,  SPIDERS,  MITES  AND  TICKS     215 

The  common  chicken-mites,  Dermanyssus  gallinaz,  are  about 
i  mm.  long,  light  gray  or  whitish  in  color,  but  becoming  quite 
red  when  full  fed.  They  hide  away  in  any  crack  or  corner 
where  they  can  find  shelter  during  the  day,  and  come  out  at 
night  to  feed.  When  numerous  they  may  be  serious  pests  to 
other  animals  as  well  as  chickens.  Cleanliness  will  prevent 
infection.  A  thorough  spraying  with  kerosene  or  strong 
kerosene  emulsion  will  kill  all  that  are  reached  by  the  oil. 
Whitewash  helps  some.  A  poorly  constructed,  badly  infected 
house  should  be  burned.  Smooth  roosts  supended  on  wires  or 
small  iron  rods  afford  few  hiding  places  for  the  mites. 


CHAPTER  XX 

OYSTERS,    CLAMS,    MUSSELS,    OTHER    MOLLUSCS, 
AND  THE  SHELL-FISH  INDUSTRIES 

The  oysters,  clams,  mussels  and  snails,  the  molluscs  (branch 
Mollusca)  with  which  we  are  most  familiar,  have  their  soft 
bodies  protected  by  a  firm  outer  shell  which  is  formed  of  car- 
bonate of  lime.  But  the  slugs,  which  are  common  in  the  garden 
and  in  moist  places,  the  beautiful  sea-slugs  or  nudibranchs, 
which  are  found  in  salt  water,  and  the  cuttlefish  and  octopi, 
which  are  also  marine,  all  of  which  also  belong  to  this  branch, 
are  not  protected  by  such  a  shell.  In  habits  and  distribution 
the  members  of  this  branch  vary  as  much  as  they  do  in  structure 
and  general  appearance.  Many  of  the  snails  and  slugs  live 
on  land,  feeding  on  live  or  dead  and  decaying  vegetable  tissue. 
Most  of  the  mussels  live  in  fresh  water,  but  all  the  other 
members  of  the  branch  live  in  the  sea,  some  at  the  surface, 
others  at  moderate  or  great  depths,  many  in  the  sand  or  mud  of 
shores  and  shallow  bottoms. 

The  Fresh-water  Mussels. — A  study  of  the  fresh-water 
mussel  will  give  one  a  general  idea  of  the  structure  of  the  typical 
members  of  this  branch.  The  two  valves  of  the  shell  are  held 
together  along  the  dorsal  edge  by  the  horny  hinge-ligaments. 
Toward  the  rounded  anterior  end  there  is,  on  each  valve,  a 
prominent  elevation,  the  umbo,  which  marks  the  oldest  part  of 
the  shell,  and  from  which  extends  a  series  of  concentric  lines 
of  growth.  When  the  mussel  is  feeding  in  the  bed  of  the  stream 
the  anterior  end  is  buried  deep  in  the  mud  and  only  a  little  of 
the  posterior  end  is  exposed.  The  valves  are  opened  slightly 
at  the  posterior  end,  and  between  them  may  be  seen  the  edges 
of  the  mantle  that  covers  the  soft  body  and  lines  the  inside  of 
the  shell.  When  one  of  the  valves  is  removed  it  will  be  seen 
that  the  mantle  is  attached  to  the  inner  surface  of  the  shell  a 

216 


hinge  ligament  K 

right  auricle 

anterior  aorta  \  \ 
reno-perlcardial  aperture  ^ 

renal  aperture .. 
genital  aperture    x 


umbone 
hinge  tooth--. 


stomach- 
digestive  gland. 


gullet 

cerebw-plc'iiral  ganglion  -  -.$'-.* 
month  — 


anter  adductor^' 

anter  retractor   , 
pedal  ganglion 


foot 


intestine'" 
typhlosole'' 


Fir,.   99. — Dissection  of  ;i  fn 


ventricle 


pericardium 


rectum 
^kidney 

f,* '-dorsal  pall/al  aperture 
.-  posterior  aorta 
i post,  retractor 


mantle 


mantle  cavity 


post  adductor 
anus 


visceral  ganglion 

exhalant  siphon 
super  branchial  chamber 

-  right  gill 


-inhalant  siphon 


shell 


•pallial  groove 


ter  mussel,  I'nio  sp. 


OYSTERS,  CLAMS,  MUSSELS  217 

short  distance  from  the  edge.  The  crease  on  the  shell  indicat- 
ing this  line  of  attachment  is  called  the  pallial  line.  Near  the 
anterior  end  of  the  inner  surface  of  the  valve  is  a  rather  large 
distinct  impression.  This  is  the  point  of  attachment  of  the 
(interior  adductor  muscle.  Just  behind  and  above  this  is  the 
smaller  impression  of  the  anterior  retractor  muscle,  and  behind 
and  below  it  is  the  impression  of  the  protractor  muscle.  At 
the  other  end  of  the  valve  is  the  large  impression  of  the  poste- 
rior adductor  muscle  and  the  small  impression  of  the  posterior 
retractor  muscle.  The  anterior  and  posterior  adductor  muscles 
extend  from  one  valve  to  the  other  and  when  they  contract 
the  edges  of  the  two  sides  of  the  shell  are  held  close  together. 
When  these  muscles  are  relaxed  the  valves  are  opened  slightly 
by  the  strong  hinge  ligament  which  is  stretched  tightly  when 
the  valves  are  closed.  The  retractor  and  protractor  muscles 
govern  the  movement  of  the  foot. 

Where  the  mantle  covers  the  body  it  is  a  thin  delicate  mem- 
brane, but  the  free  part,  below  the  pallial  line,  is  somewhat 
heavier,  and  the  edges  are  thicker.  At  the  posterior  end  the 
thickened  fringed  portions  of  the  two  mantle  lobes  form  two 
short  tubes,  the  inhalant  and  exhalant  siphons.  The  cilia  on 
the  fringes  of  the  mantle  cause  a  current  of  water  to  flow  in 
through  the  lower  or  inhalant  siphon  into  the  mantle  cavity, 
the  space  inclosed  by  the  mantle  lobes.  Here  the  water  bathes 
the  inner  surface  of  the  mantle  and  the  gills,  and  passes 
through  the  gills  to  a  space  just  above  them  known  as  the 
supra-branchial  cavity.  In  this  space  it  passes  backward  again 
and  out  through  the  upper  or  exhalant  siphon.  The  mantle 
is  an  important  organ  of  respiration,  for  as  in  the  gills  of  fishes, 
oxygen  is  taken  from  the  water  and  carbon  dioxide  passed  out 
through  its  thin  delicate  walls.  The  shell  is  the  product  of  the 
secretions  of  the  mantle.  Over  its  whole  surface  the  mantle  is 
constantly  secreting  a  thin  layer  of  carbonate  of  lime  which 
serves  to  thicken  the  older  parts  of  the  shell  and  to  extend  and 
harden  the  thin  soft  margins. 

When  the  mantle  is  removed  from  one  side  of  the  body  the 
large  muscular  foot,  the  thin  delicate  leaf-like  gills  and  the  soft 
visceral  mass  of  the  body  are  exposed.  The  foot  is  large  and 


218    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

quite  firm,  somewhat  triangular  in  shape,  and  is  capable  of 
being  extended  beyond  the  edges  of  the  shell  for  a  considerable 
distance.  It  is  by  means  of  this  organ  that  the  animal  plows 
its  way  through  the  mud  or  sand  in  which  it  lives.  The  gills 
are  two  pairs  of  flattened,  ribbed,  membranous  folds  which  hang 
down  into  the  mantle  cavity  from  each  side  of  the  body.  The 
water  bathing  these  gills  and  passing  up  between  them  comes 
in  very  close  contact  with  the  minute  blood-vessels  with  which 
the  gills  are  abundantly  supplied  so  that  the  transfer  of  gases 
from  the  water  to  the  blood  and  from  the  blood  to  the  water 
can  readily  take  place.  The  body  is  not  divided  into  well- 
defined  regions.  Just  below  and  back  of  the  anterior  adductor 
muscle  is  the  mouth  opening.  On  each  side  of  it,  looking  some- 
what like  little  gills,  are  two  pairs  of  labial  palpi  whose  function 
it  is  to  convey  to  the  mouth  the  minute  plant  or  animal  organ- 
isms that  are  carried  in  by  the  water.  Through  a  short  esopha- 
gus these  particles,  which  are  the  food  of  the  mussel,  pass 
into  a  rather  large  stomach  and  from  that  into  a  long  narrow 
intestine  which  is  coiled  in  the  base  of  the  foot  and  the  visceral 
mass.  The  posterior  part  of  the  alimentary  canal,  the  rectum, 
is  a  long  straight  tube  extending  through  the  pericardium  and 
opening  into  the  supra-branchial  cavity  close  to  the  exhalant 
siphon. 

The  pericardium  is  the  space  in  the  upper  portion  of  the 
visceral  mass  just  below  the  hinge-ligament.  It  is  covered  by 
a  delicate  membrane,  and  contains  the  heart  and  some  of  the 
blood-vessels.  The  heart  consists  of  a  single  ventricle,  which 
surrounds  part  of  the  rectum,  and  a  right  and  left  auricle. 
When  the  ventricle  contracts  it  sends  the  blood  forward  and 
backward  through  large  blood-vessels,  the  anterior  aorta  and 
the  posterior  aorta.  Part  of  the  blood  is  carried  directly  to  the 
mantle  where  it  is  aerated  and  then  returned  to  the  heart.  The 
rest  of  the  blood  is  carried  to  various  parts  of  the  body  and 
finally  collects  in  a  space,  the  vena  cava,  just  beneath  the  peri- 
cardium. From  the  vena  cava  the  blood  passes  into  the  excre- 
tory organs,  the  kidneys,  which  lie  just  beside  it,  and  on  down 
into  the  gills  and  finally  back  to  the  heart  where  it  enters  the 
auricles. 


OYSTERS,  CLAMS,  MUSSELS  219 

Instead  of  a  series  of  ventral  ganglia  and  a  more  or  less 
specialized  brain  as  is  found  in  the  insects,  worms  and  some 
other  invertebrates,  the  nervous  system  of  the  mussel  consists 
of  three  scattered  principal  groups  of  ganglia  connected  by 
nerve  cords.  Lying  one  on  each  side  of  the  esophagus  are  the 
cerebro-pleural  ganglia.  They  are  connected  with  each  other 
by  a  nerve  which  passes  over  the  esophagus,  and  by  larger 
nerves  with  the  pedal  ganglion  in  the  foot  and  the  visceral 
ganglion  which  lies  near  the  posterior  adductor  muscle. 

The  sexes  of  the  mussels  are  separate,  that  is  the  ova  and 
spermatozoa  are  produced  in  different  individuals,  but  the 
reproductive  glands,  or  gonads,  of  the  two  sexes  are  very  similar. 
They  form  a  glandular  mass  of  tissue  filling  the  base  of  the  foot. 
The  ducts  from  the  ovaries  and  testes  open  near  the  base  of  the 
gills.  The  spermatozoa  are  carried  from  the  body  with  the 
water  that  passes  out  through  the  exhalant  siphon,  and  find 
their  way  to  another  mussel  with  the  incoming  water  currents. 
The  eggs  pass  into  the  supra-branchial  chamber,  but  instead  of 
passing  on  out  of  the  body  remain  there  until  they  are  fertilized 
by  the  spermatozoa  from  another  individual.  They  then 
drop  down  into  the  outer  gills,  which  serve  as  brood  chambers. 
Here  the  young  are  held  for  some  time,  and  develop  bivalve 
shells  which  enclose  them.  In  some  species  the  margin  of  the 
shell  is  provided  with  stout  hooks,  but  in  others  it  is  without 
them.  Thus  armed,  the  young,  or  glochidia,  as  they  are  called, 
pass  into  the  water.  When  touched  the  shell  closes  quickly 
and  firmly.  If  the  young  come  in  contact  with  the  fins  or  gills 
of  a  fish  the  snapping  shut  of  the  shell  may  serve  to  attach  them 
to  it.  The  forms  with  hooks  on  their  shells  are  more  often 
found  on  the  fins  of  the  fish,  the  bookless  kind  on  the  gills. 
Once  attached,  their  presence  causes  an  irritation  of  the  tissues 
of  their  host  which  results  in  a  growth  or  cyst  that  soon  covers 
them  over.  In  this  condition  they  remain  for  some  time, 
drawing  their  nourishment  from  the  host  and  undergoing  the 
transformations  that  change  them  to  small  mussels  which  fi- 
nally drop  to  the  mud  where  they  continue  their  growth,  feed- 
ing on  small  organisms,  both  plant  and  animal,  which  are 
taken  from  the  water  entering  th,e  mouth  cavity.  The 


220    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

knowledge  of  this  relation  of  the  fish  to  the  mussel  is  of  prime 
importance  in  the  attempts  that  are  being  made  to  restock 
some  of  the  mussel  beds  that  have  been  depleted  on  account 
of  £he  increased  demand  for  the  shells  for  the  making  of 
pearl  buttons. 

Mussels  and  Buttons. — Until  about  1891  no  use  was  made 
of  the  shells  of  fresh-water  mussels.  But  at  this  time  it  was 
found  that  excellent  pearl  buttons  could  be  made  from  these 
shells,  and  so  there  has  sprung  up  an  industry  spread  through- 
out the  central  part  of  the  United  States  that  has  a  value  of 
more  than  $6,000,000  annually  and  gives  employment  to 
hundreds  of  people.  The  Government  has  established  a  station 
for  the  propagation  of  mussels  in  order  that  depleted  streams 
may  be  restocked  and  new  areas  made  productive.  Mussels 
containing  the  developing  glochidia  are  teased  up  in  water  and 
this  water  is  poured  into  tanks  containing  fish.  When  their  fins 
and  gills  are  well  covered  with  the  glochidia  the  fish  are  liber- 
ated in  the  streams  that  are  to  be  stocked  with  the  mussels. 

Mussels  and  Pearls. — In  an  earlier  chapter  reference  has 
been  made  to  the  fact  that  pearls  are  produced  in  many  mol- 
luscs by  the  pearly  nacreous  substance,  of  which  the  shell  is 
formed,  being  deposited  around  certain  parasitic  worms  that 
are  found  in  the  body  of  the  animal.  When  such  secretions 
are  irregular  in  shape  they  are  usually  called  baroques,  or  slugs. 
When  round  or  pear-shaped,  or  of  some  other  regular  shape, 
they  are  called  pearls. 

It  is  not  an  uncommon  thing  to  find  baroques  or  slugs  in  the 
fresh-water  mussels,  some  of  them  very  beautiful.  These  are 
usually  formed  around  certain  parasitic  flat  worms,  a 
Distomid  having  the  muskrat  or  otter  as  one  of  its  hosts,  being 
a  common  form. 

Perfect  round  pearls  of  delicate  luster  and  great  value  are 
also  often  found.  Recent  investigations  have  shown  that  the 
egg  or  the  dead  body  of  a  small  water-mite  may  form  the  nu- 
cleus around  which  the  pearl  is  formed,  the  most  perfect 
pearls  probably  being  formed  around  the  eggs.  These  mites, 
Unionicola  (Atax),  liveparasitically  in  the  gills  or  mouth  cavity 
of  the  mussel,  and  when  they  lodge  in  the  tissues  in  such  a  way 


OYSTERS,  CLAMS,  MUSSELS 


221 


as  to  cause  irritation,  the  mussels,  as  a  means  of  protection, 
cover  them  over  with  the  pearly  layer.  These  pearls  vary  in 
value  from  a  few  cents  or  dollars  up  to  hundreds  of  dollars. 
Perhaps  the  most  famous  of  all  the  fresh-water  pearls  is  the 
"Queen  Pearl,"  which  was  found  in  a  New  Jersey  stream  in 
1857.  It  was  sold  by  the  finder  for  $1500,  but  is  now  valued 
at  about  $10,000.  Occasionally  some  particularly  valuable 
pearls  will  be  found  in  a  new  region,  and  during  the  "pearl 
fever"  that  follows,  thousands  of 
dollars  worth  of  pearls  may  be 
found,  but  the  mussel  beds  of  the 
streams  are  usually  almost  or 
quite  depleted.  Formerly  the 
shells  thus  gathered  were  left  on 
the  bank  to  disintegrate,  but 
they  are  now  used  in  the  impor- 
tant button  industry. 

Fresh-water  mussels  are  some- 
times used  for  food.  The  great 
shell  heaps,  or  "kitchen  mid- 
dens," found  in  many  places 
show  that  they  must  have 
formed  an  important  part  of  the 
food  of  the  early  inhabitants  of 
this  and  other  countries 

Classes  of  Mollusca. — The 
branch  Mollusca  (L.  mollis,  soft) 
is  divided  into  five  classes.  The 
class  Pelecypoda  (Gr.  pdekys,  axe, 
pous,  foot)  is  the  largest  and  most  important  group,  including 
the  mussels,  clams  and  oysters  and  others  that  furnish  an 
abundance  of  cheap,  palatable  and  nutritious  food.  The  name 
Pelecypoda  means  "hatchet-foot,"  and  refers  to  the  fleshy  foot 
or  organ  that  enables  the  clams  and  mussels  to  dig  or  plow 
their  way  through  the  mud.  The  name  Lamellibranchia,  re- 
ferring to  the  lamella-like  gills  on  each  side  of  the  body,  was 
formerly  used  for  this  class.  As  all  the  members  of  the  class 


FIG.  100. — A  chiton,  Isch- 
nochiton  magdalenen sis . 
(Reduced.) 


222    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

are  inclosed  in  a  shell  composed  of  two  parts  or  valves  they  are 
commonly  referred  to  as  bivalves. 

The  class  Gastropoda  (Gr.  gaster,  stomach;  pous,  foot)  in- 
cludes the  snail,  slugs,  periwinkles  and  many  other  molluscs 
that  are  either  naked  or  furnished  with  a  shell  composed  of  a 
single  piece. 

The  Cephalopoda  (Gr.  kephale,  head;  pous,  foot)  include 
squids,  octopi,  cuttlefish  and  the  nautilus. 

The  members  of  the  classes  Amphineura  (Gr.  amphi,  around; 
neuron,  nerve)  and  Scaphopoda  (Gr.  skaphe,  hollow;  pous,  foot) 
are  much  less  common  and  are  of  little  or  no  economic  impor- 
tance. The  first  includes  the  chitons,  which  have  segmented 
shells  and  are  fairly  common  on  rocks  on  the  California  coast. 
The  tooth-shells  sometimes  found  along  the  northern  sea 
beaches  belong  with  the  peculiar  somewhat  worm-like  mem- 
bers of  the  class  Scaphopoda. 

CLASS  PELECYPODA 

The  Mussels. — They  are  many  genera  and  species  of  fresh- 
water mussels,  and  they  are  to  be  found  in  suitable  streams 
and  lakes  in  almost  all  parts  of  the  United  States.  Their  life 
history  and  importance  have  just  been  discussed.  The  salt- 
water mussels  differ  from  those  in  fresh  water  in  several 
respects,  the  most  noticeable  of  which  is  in  shape  and  in  the 
presence  of  a  number  of  fine  tough  threads,  the  byssus,  which 
serve  to  attach  the  mussels  to  rocks  or  other  substances  on 
which  they  are  growing.  These  mussels  often  occur  in  great 
masses  over  the  rocks  and  piles  or  on  tide  flats  wherever  they 
can  find  a  place  to  attach  themselves.  They  are  often  serious 
pests  on  oyster  beds,  occurring  in  such  numbers  as  to  smother 
the  oysters  or  starve  them  by  taking  a  large  part  of  the  food 
that  would  otherwise  go  to  the  oysters.  The  salt-water  mussels 
are  often  used  for  food,  and  can  advisably  be  thus  used  more 
than  they  are  at  present.  They  occur  in  abundance  on  both 
Atlantic  and  Pacific  coasts  of  our  country,  and  are  easily 
gathered  at  low  tide. 

Clams. — In  most  of  the  clams  the  portion  of  the  mantle  that 
forms  the  siphons  in  the  mussels  is  especially  developed  and 


OYSTERS,  CLAMS,  MUSSELS 


223 


produced  into  a  long  neck-like  process.  This  enables  the  clam 
to  bore  into  the  mud  or  sand  for  some  distance  and  still 
keep  the  end  of  the  siphon  in  the  water.  Those  who  have 
never  been  near  the  sea-shore  where  they  could  take  part  in  a 
clam-bake  have  at  least  enjoyed  their  clam  chowder  in  their 
inland  homes  even  if  it  were  made  from  the  canned  article. 
Hardly  a  beach  along  any  of  our  coast  lines  but  furnishes  an 
abundance  of  one  or  more  species  of  clams.  Along  the  North 
Atlantic  coast  the  soft  clam,  Mya  arenaria,  is  one  of  the  most 


FIG.  101. — The  common  sea-mussel,  Mytilus  edulis  L.     (Reduced.) 

important  of  the  clams.  At  one  time  it  occurred  in  seemingly 
unlimited  numbers,  but  on  account  of  wasteful  and  destructive 
methods  of  gathering  them  many  of  the  best  beds  are  now 
nearly  depleted.  Most  of  these  tide  flats  may  be  made  to 
yield  abundant  supplies  again  under  the  methods  of  cultiva- 
tion and  protection  that  are  now  being  adopted  in  some 
places. 

The  hard  clam,  or  quohog,  or  little-neck  clam,  Venus 
mercenaria,  is  the  most  important  clam  from  New  York  south- 
ward. Unlike  the  soft  clam,  whose  shell  is  comparatively 
light  and  often  does  not  close  tightly  along  the  edge,  the  hard 
clam  has  a  heavy  shell  that  closes  very  firmly. 


224    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


Other  species  of  clams  and  two  or  more  kinds  of  scallops, 
Pecten,  occurring  along  the  Atlantic  coast,  are  used  for  food. 
The  scallops  differ  from  the  clams  in  having  deep  grooves 
radiating  from  the  hinge  to  the  edge  of  the  shell.  Some  are 
beautifully  colored.  The  meat  of  many  of  them  is  very  dainty. 

The  soft  clam  has  been  in- 

troduced  into  the  waters  of 
the  Pacific  Coast  States,  doubt- 
less with  the  shipments  of 
eastern  oysters.  There  it  is 


FIG.  102.— Soft-shell 
clam,  Mya  arenaria  L. 
(Reduced.) 


FIG.  103. — A  geoduck  or 
giant  cla.m,Glycimeris  generosa, 
which  attains  a  weight  of  five 
or  six  pounds.  (M  u c h 
reduced.) 


known  as  the  "eastern"  clam,  but  has  not  yet  found 
much  favor  in  the  markets  because  there  are  several  native 
species  that  are  more  in  demand.  One  of  the  most  common 
of  these  is  the  hard  shell  or  little-neck,  Tapes  staminea, 
which  seems  to  take  the  place  of  the  hard  clam  of  the  east 
coast.  The  great  Washington  clam,  Schizotharus  nuttalli,  and 
the  butter-clam,  Saxidomus  nuttalli,  are  common  in  many 
places  on  the  northwest  coast.  One  of  the  most  remarkable 
clams  in  the  United  States  is  the  giant  "geoduck"  (earth 
duck),  Glycimeris  generosa,  which  sometimes  weighs  as  much  as 


OYSTERS,  CLAMS,  MUSSELS  225 

six  pounds  and  has  a  siphon  that  may  be  extended  eighteen  to 
twenty-four  inches.  The  body  is  very  large,  but  the  shells  are 
so  small  that  they  only  cover  the  sides  of  the  clam  and  the 
great  white  mass  that  extends  beyond  the  shells  and  the  long 
siphon  looks  not  unlike  the  breast  and  neck  of  a  duck,  the 
shells  representing  the  folded  wings. 

In  the  hard,  smooth,  wave-beaten,  sandy  beaches  of  the 
North  Pacific  are  to  be  rjund  the  "razor-clams,"  Machera 
patula,  which  are  undoubtedly  the  finest  of  all  the  clams. 
The  meat  is  white  and  tender  and  most  delicately  flavored. 
The  canneries  tnat  have  been  established  along  the  coast  are 
fast  depleting  the  supply  of  these  choice  clams. 

Oysters. — Much  more  important  than  the  clams,  though 
less  numerous,  are  the  oysters,  two  species  of  which  occur 
along  our  coasts  and  are  used  for  food.  Some  of  the  most 
extensive  natural  beds  occur  in  Chesapeake  Bay,  but  other 
beds  are  found  as  far  north  as  Prince  Edwards  Island  and  as 
far  south  as  the  Gulf  States.  Many  excellent  beds  are  found 
in  Long  Island  Sound.  The  eastern  oyster,  Ostrea  virginiana, 
is  unisexual,  that  is,  the  ova  and  spermatozoa  are  produced  in 
different  individuals.  During  spawning  season  the  female 
produces  sixteen  to  sixty  millions  of  ova  which  are  set  free  in 
the  water  to  meet  by  chance  the  spermatozoa  from  the  male. 
If  this  union  takes  place,  the  ova  are  fertilized  and  soon  lose 
their  original  pear  shape  and  become  quite  round.  If  they 
are  not  fertilized  they  soon  perish.  Within  two  or  three  hours 
after  fertilization  these  ova,  which  are  single  cells  too  small  to 
be  detected  with  the  unaided  eye,  begin  to  divide,  and  in  two 
hours  more  have  changed  from  single  round  cells  into  masses 
of  cells,  the  masses  themselves  being  rounded  and  about  the 
size  of  the  original  egg  cell.  A  little  later,  small  thread-like 
projections,  or  cilia,  begin  to  appear  on  one  side.  The  embryos 
have  now  reached  the  swimming  stage,  for  by  means  of  these 
cilia  they  are  able  to  move  about  through  the  water  at  will. 
They  remain  in  this  stage  from  three  to  six  days,  or  until  the 
shells  have  begun  to  form,  when  they  sink  to  the  bottom,  and, 
if  they  are  fortunate  enough  to  strike  some  suitable  hard  object, 
they  become  attached  and  begin  to  take  on  the  character  of  an 
15 


226    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

adult  oyster.  From  this  time  on  the  young  oysters  are  less 
exposed  to  danger,  but  the  number  of  them  that  reach  maturity 
is  very  small  when  compared  with  the  number  that  perish  or 
are  destroyed  in  one  way  or  another. 

The  young  oysters  when  first  attached  are  called  "spat"; 
when  a  little  older  this  spat,  now  called  "seed,"  may  be  trans- 
planted to  new  beds,  which  are  stocked  in  this  way. 


FIG.  104. — Young  (spat)  of  the  west-coast  oyster,  Ostrea  lurida,  attached 
to  rock.     (Reduced.) 

In  some  regions  clean  shells  or  other  "cultch"  are  distributed 
over  the  beds  just  before  the  spawning  season  in  order  that 
there  may  be  plenty  of  clean  hard  surfaces  for  the  young  em- 
bryos. The  oysters  are  ready  for  market  in  from  three  to  five 
years,  and  are  gathered  from  their  beds  by  means  of  long- 
handled  tongs  or  dredged  up  by  means  of  dredges  and  power 


OYSTERS,  CLAMS,  MUSSELS  227 

boats.  It  has  been  estimated  that  more  than  twenty-five 
million  bushels  of  oysters  are  gathered  from  the  beds  in  the 
United  States  each  year. 

The  west-coast  oyster,  Ostrea  lurida,  is  much  smaller  than 
the  eastern  oyster  and  has  a  much  thinner  shell.  It  differs  also 
in  being  hermaphroditic  and  viviparous;  that  is,  both  ova  and 
spermatozoa  are  produced  in  the  same  individual  and  the  eggs 
are  fertilized  in  the  gill  and  mantle  cavities  and  here  also  they 
pass  through  the  early  stages  of  development.  At  spawning 
season,  when  these  young  embryos  are  set  free,  they  have 
already  reached  the  swimming  stage  and  are  soon  ready  to 
attach  themselves  to  some  convenient  shell  or  other  collector, 
where  they  remain  fixed  through  life. 

The  area  available  for  oyster  cultivation  is  much  less  on  the 
Pacific  coast  than  on  the  Atlantic,  but  the  total  output  of 
oysters  from  the  state  of  Washington  amounts  to  about 
$300,000  annually.  Many  years  ago  shipments  of  eastern 
oyster  spat  or  seed  were  made  to  the  Pacific  coast  and  planted 
in  San  Francisco  Bay  where  they  were  allowed  to  remain  until 
they  reached  a  marketable  size.  Now  many  carloads  are 
shipped  from  the  east  each  season  and  planted  on  the  tide  flats 
in  California  and  Washington,  the  introduced  oysters  attaining 
a  good  size  and  a  flavor  hardly  excelled  in  their  native  waters. 
On  account  of  the  low  temperature  of  the  water  during  the 
spawning  season  most  of  the  young  of  the  eastern  oyster  are 
killed  while  they  are  swimming  at  the  surface,  and  so  the  beds 
of  eastern  oysters  have  to  be  replanted  when  the  marketable 
oysters  are  removed. 

There  are  two  common  species  of  oysters  native  to  Europe. 
The  smaller  flat  oyster,  Ostrea  edulis,  occurs  along  the  northern 
shores,  and  in  many  respects  resembles  our  Pacific  coast  oyster. 
Like  the  latter  it  is  hermaphroditic.  The  Portuguese  oyster, 
0.  angulata,  is  found  on  the  southern  shores  and  resembles 
more  our  east-coast  oyster  in  size  and  methods  of  breeding,  but 
is  not  so  highly  esteemed  for  food  as  the  smaller  northern 
oyster. 

The  European  oysters  have  been  cultivated  since  the  earliest 
times,  and  in  many  places  the  collecting  of  the  spat  on  especi- 


228    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

ally  prepared  collectors,  the  transplanting  and  caring  for  the 
seed  and  the  final  marketing  of  the  oyster  after  it  has  been 
fattened  and  often  flavored  to  suit  the  taste  of  a  fastidious 
public,  furnishes  employment  to  many  people  along  the  sea 
coasts. 

Many  other  species  occur  in  other  parts  of  the  world,  where 
they  are  usually  important  articles  of  food. 

Shell-fish  and  Disease. — In  feeding,  the  oysters,  clams  and 
mussels  may  take  into  their  body  any  minute  particles  that  are 
to  be  found  in  the  water  where  they  are  lying.  Thus  it  will  be 
seen  that  any  impurities  that  are  in  the  water  may  readily 
affect  the  bivalves  living  in  it.  It  sometimes  happens  that 
oyster  or  clam  beds  are  situated  so  near  the  outfalls  of  sewers 
from  some  city  that  the  water  is  always  polluted.  Shell-fish 
corning  from  such  places  are  usually  plump  and  look  most  in- 
viting, but  as  they  may  contain  typhoid  germs  and  other  dan- 
gerous organisms  they  are  to  be  avoided.  The  interest  that 
has  been  aroused  in  this  subject  during  the  last  few  years  has 
been  the  cause  of  much  careful  study,  and,  while  the  danger  is  a 
very  real  one,  the  rigid  supervision  that  is  now  kept  over  many 
of  the  sources  from  which  this  important  food  supply  comes, 
makes  most  shell-fish  safe.  If  they  are  thoroughly  cooked 
before  being  eaten  the  harmful  organisms  are  destroyed.  Oy- 
sters that  have  been  "freshened"  or  bloated  by  being  trans- 
ferred to  fresher  water  for  a  few  days  or  hours  should  never  be 
eaten  raw,  as  the  places  where  this  process  is  carried  on  are  too 
often  in  dangerous  proximity  to  sewer  outfalls.  A  strong 
public  sentiment  against  such  practice  will  insure  its  discon- 
tinuance. 

Pearl-oysters. — The  "pearl-oyster"  of  the  South  Seas  is 
really  not  very  closely  related  to  our  oysters.  It  is  more  of  the 
shape  of  our  common  pectens,  and  has  a  strong  byssus  by 
which  it  attaches  itself,  at  least  during  its  earlier  stages,  to 
rocks  or  corals.  The  shell  of  some  species  is  quite  heavy,  and 
the  wonderfully  iridescent  inner  layer  is  known  as  "  mother-of- 
pearl.  "  The  pearl-shells  form  an  important  article  of  com- 
merce, as  the  mother-of-pearl  is  used  in  the  manufacture  of 
many  articles.  The  pearls  themselves,  which  are  formed  in 


OYSTERS,  CLAMS,  MUSSELS 


229 


the  same  way  as  that  already  described  for  the  fresh- water 
pearls,  may  have,  when  large  and  of  perfect  shape  and  luster, 
a  very  great  value.  The  recently  attained  perfection  in  the 
making  of  imitation  pearls  may  somewhat  lessen  the  market 
value  of  true  pearls,  but  the  pearl-fisheries  are  still  of  great 
importance. 

For  more  than  two  thousand  years  Ceylon  has  been  the 
center  of  the  pearl-fisheries  industry,  but  many  valuable  pearls 
and  much  better  mother-of-pearl  shells  are  found  in  the  waters 
of  other  tropical  islands. 


FIG.  105. — Inner  side  of  a  pearl  shell.     (Reduced). 

Teredos. — Very  unlike  any  other  members  of  this  class  in 
general  appearance  and  habits  are  the  teredos  or  ship-worms 
that  so  often  do  great  damage  to  any  timber  that  is  in  salt 
water.  The  young  teredo  is  a  free-swimming  embryo  like  the 
young  of  other  molluscs,  but  it  soon  settles  on  some  piece  of 
submerged  wood  and  begins  to  burrow  into  it.  As  it  grows 
and  develops  its  small  bivalve  shell,  it  bores  deeper  into  the 
wood,  lining  its  burrow  with  a  shell-like  calcareous  deposit. 
As  the  ends  of  the  siphons  are  kept  close  to  the  entrance  of 
the  burrow,  the  animals  soon  become  very  much  elongated  and 


23o    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

worm-like,  and  indeed  are  more  commonly  thought  to  be  worms 
than  bivalve  molluscs.  They  bore  into  the  wood  only  for 
protection,  and  do  not  feed  upon  it.  Their  food  consists  of 
minute  organisms  that  are  taken  into  the  body  through  the 
siphons. 

Teredos  are  very  serious  pests  on  the  piles  of  wharves,  and 
on  dykes,  ships'  bottoms  and  any  other  wood  that  comes  in 
contact  with  salt  water.  In  some  places  they  are  so  abundant 
that  a  two-inch  plank  may  be  completely  honey-combed  and 
destroyed  in  less  than  a  year.  The  only  protection  is  to  cover 
the  wood  with  some  substance  which  the  teredo  cannot  or  will 
not  penetrate.  Heavy  coatings  of  copper  or  verdigris  paint 
are  often  used,  but  they  must  be  reapplied  frequently.  Cer- 
tain other  Pelecypod  molluscs  have  the  remarkable  habit  of 
boring  into  solid  rocks  far  enough  to  protect  them. 

CLASS  GASTROPODA 

Snails. — Snails  are  very  common  objects  in  water  and  on 
land.  They  all  have  shells,  which  may  be  conical  or  spire- 
shaped  or  flattened.  The  most  common  snails  have  spiral, 
more  or  less  cone-shaped  shells.  One  group,  the  pulmonate 
snails,  including  many  common  aquatic  and  terrestrial  forms, 
do  not  breathe  by  means  of  gills  as  do  most  other  molluscs. 
On  the  right  side  of  the  body  near  the  anterior  end  is  an  exter- 
nal opening  that  leads  into  a  sac,  the  so-called  "lung."  The 
inner  surface  of  this  sac  is  abundantly  supplied  with  fine  blood- 
vessels through  the  walls  of  which  oxygen  is  taken  from  the 
air  and  carbon  dioxide  thrown  off.  These  snails  are  vege- 
table feeders  and  are  sometimes  serious  pests  among  flowers 
and  in  the  garden. 

The  members  of  another  group  of  common  pond  snails 
have  gills  and  no  lung-sac.  These  live  on  the  bottom  of  the 
ponds  and  feed  on  animal  rather  than  vegetable  food. 

Most  of  the  snails  and  the  slugs  have  two  pairs  of  "  horns' ' 
with  the  eyes  on  the  tips  of  the  second  pair.  Some  snails  have 
only  one  pair,  which  are  used  as  feelers,  the  eyes  being  situated 
at  the  base  of  these  feelers. 


OYSTERS,  CLAMS,  MUSSELS  231 

Slugs. — The  small  slimy  slugs  that  are  often  so  common  in 
moist  places  are  very  serious  pests  in  vegetable  and  flower 
gardens.  They  hide  away  in  some  cool,  dark  place  during  the 
day,  and  at  night  come  out  and  feed  upon  any  succulent  plants 
that  they  can  find.  They  do  particular  damage  to  early  young 
plants,  often  destroying  them  as  fast  as  they  come  up.  No 
very  efficient  remedy  has  been  suggested,  but  their  numbers 
may  be  somewhat  reduced  by  one  or  more  of  the  following 
methods.  The  ground  around  the  plants  should  be  examined 
for  the  slugs,  which  may  easily  be  destroyed.  If  ashes  or  air- 
slaked  lime  is  then  spread  about  the  plants  the  slugs  will  not 
bother  them  as  long  as  the  ashes  or  lime  remains  perfectly  dry 


FIG.  1 06. — The  giant  yellow  slug  of  California,  Ariollmax  californica. 
(This  slug  reaches  a  length  when  outstretched  of  twelve   inches.) 

and  does  not  form  a  crust  over  which  the  slugs  can  crawl. 
Boards  or  stones  afford  good  hiding  places  and  may  be  placed 
in  the  garden  as  traps  to  be  examined  each  day.  Lettuce  or 
cabbage  leaves  thrown  on  the  ground  are  attractive  baits  and 
are  also  good  hiding  places  which  can  be  easily  examined  every 
morning.  If  the  plants  are  examined  at  night  writh  the  aid  of 
a  lantern  many  of  the  slugs  may  be  found  and  destroyed. 
Spraying  with  arsenate  of  lead  or  kerosene  emulsion  does  some 
good,  the  first  poisoning  the  slugs,  the  latter  killing  those  that 
it  touches  and  being  more  or  less  effective  as  a  repellent. 

Marine  Gastropods. — Hundreds  of  shell-forming  Gastropods 
are  found  along  every  sea-shore.  These  present  a  wonderful 
variety  of  shape  and  size  and  color.  Some  of  them  are  most 
beautifully  colored  and  fantastically  shaped.  The  great  cow- 
ries with  their  delicately  colored  porcelain-like  shells,  the  lim- 


23 2    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

pets  so  common  on  the  rocks  everywhere,  the  helmet-shells 
from  which  cameos  are  cut,  and  hosts  of  others  all  belong  to 
this  group.  The  large  sea-snails  and  the  much  smaller  but 
more  numerous  drills  (family  Muricidce)  are  often  of  serious 
economic  importance.  The  sea-snails  bore  holes  by  means  of 
their  roughened  tongue-like  organ,  the  radula,  and  an  acid 
salivary  secretion  through  even  the  thickest-shelled  clams,  and 
suck  out  the  soft  body  of  the  victim.  The  oyster-drills,  of  the 
genus  Urosalpinx  and  of  other  genera,  drill  holes  through 
the  oyster  shells  in  the  same  manner,  and  as  they  often  occur  in 
great  numbers  on  the  oyster  beds  they  may  destroy  many 
oysters.  Some  of  them  have  a  habit  of  collecting  in  great 
masses  at  their  breeding  season,  and  are  sometimes  gathered 


FIG.  107. — Two   kinds   of   oyster-drills;     large    one,    Polynices 
Gould;  small  one,  Thais  lamellosa.     (Reduced.) 


lewis  I, 


and  used  for  food.  Many  Muricidce  when  crushed  exude  a 
reddish-purple  fluid  which  in  olden  times  was  used  as  a  dye 
famous  under  the  name  of  Tyrian  purpJe. 

Abalones,  or  ear-shells,  which  are  particularly  abundant 
along  certain  parts  of  the  California  sea-coast,  are  of  interest 
because  of  their  economic  importance.  The  animal  lives 
attached  to  a  rock  by  a  great  muscle  which  fills  most  of  the 
firm  ear-shaped  shell  that  covers  it.  The  outer  side  of  the 
shell  is  rough  and  dull-colored  but  the  inner  surface  is  smooth 


OYSTERS,  CLAMS,  MUSSELS 


233 


and  wonderfully  irridescent.  It  is  much  prized  for  making 
buttons  and  for  other  purposes  for  which  mother-of-pearl 
is  used.  Very  beautiful  and  valuable  baroque  pearls  are  some- 
times found  in  the  abalones.  The  meat  is  dried  or  canned 
and  used  for  stews  or  chowder.  Large  quantities  of  dried  or 
canned  abalone  meat  are  shipped  each  year  to  China. 

The  nudibranchs  or  sea-slugs  are  doubtless  the  most  beauti- 
ful of  all  the  molluscs.  They  are  without  a  shell,  and  the 
gills  are  usually  in  the  shape  of  delicate,  freely  projecting  tufts 
often  arranged  in  rows  along  the  back.  The  gills,  and  indeed 
the  whole  animal,  are  often  most  strikingly  and  beautifully 
colored. 


FIG.  108. — Three  Pacific  coast  nudibranchs;  Doris  tuberculata  (in 
lower  left-hand  corner),  Echinodoris  sp.  (upper  one),  and  Triopha  modesta 
(at  right). 


Squids,  Cuttlefishes  and  Octopi. — Both  in  habits  and 
structure  the  squids,  cuttlefishes  and  octopi,  or  "devil-fishes," 
differ  greatly  from  the  other  members  of  this  branch.  Most 
molluscs  move  but  little  or  not  at  all  except  as  larvae,  but  the 
Cephalopoda  are  very  active  all  their  life,  swimming  swiftly 
through  the  water.  The  name  Cephalopoda  refers  to  the  fact 
that  the  foot  assumes  the  appearance  of  a  number  of  arms  or 


234    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

appendages  of  the  head.  The  head  is  more  or  less  definitely 
set  off  from  the  rest  of  the  body.  The  eyes  are  large  and  highly 
developed.  The  main  part  of  the  foot  is  composed  of  a  series 
of  eight  or  ten  freely  movable  tentacles  or  "arms"  surrounding 
the  mouth.  These  arms  are  provided  with  numerous  sucker- 


FIG.  109. — A  devil-fish,  Polypus  apollyon.     (Much  reduced.) 

like  discs  which  enable  the  animals  to  hold  fast  to  the  rocks  or 
to  catch  and  hold  their  prey,  for  they  are  all  carnivorous. 

The  devil-fishes,  genus  Octopus  (Polypus),  have  only  eight 
arms  and  so  are  known  as  Octopods.  These  arms  or  tentacles 
may  attain  a  length  of  fifteen  feet  or  more,  and  with  their  great 
sucker-like  discs  form  very  effective  means  of  offense  or  de- 
fense. The  body  is  sub-spherical  and  without  a  shell.  Their 


OYSTERS,  CLAMS,  MUSSELS 


235 


terrifying  appearance  has  been  the  basis  for  many  weird  sea 
tales.  The  argonaut,  or  paper-nautilus,  Argonauta  argo, 
secretes  a  beautiful  thin  shell  for  the  protection  of  the  eggs. 
The  cuttlefish,  or  sepias,  and  the  squids,  have  in  addition 
to  the  eight  arms  of  the  Octopods,  two  other  long  slender 


FIG.  no. — A  squid,  Loligo  opalescens  juv.     (Reduced.) 

arms,  with  suckers  near  the  ends  only,  and  so  are  known  as 
Decapods.  The  body  is  longer  and  better  fitted  for  swimming. 
Some  of  the  squids  attain  enormous  size,  having  a  body- 
length  of  twenty  feet  and  arms  thirty  to  thirty-five  feet  long. 
The  smaller  squids  are  often  very  numerous  and  are  commonly 
used  for  bait  by  the  fishermen  of  many  regions.  The  cuttlefish 


236    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

have  in  their  body  a  horny  calcareous  substance  known  as 
the  "bone"  or  "pen."  This  is  the  cuttlefish  bone  that  is 
used  to  feed  canary  birds.  True  sepia  ink  is  also  a  product 
of  these  creatures.  The  ink  is  a  dark  secretion  which  the 
cuttlefish  discharges  when  it  is  irritated  or  frightened. 
This  clouds  the  water  and  allows  the  animal  to  escape  from 
its  enemies. 

The  chambered  pearly  nautilus,  genus  Nautilus,  belongs  to 
the  only  living  genus  of  a  group  which  was  much  better 
represented  in  former  geologic  times. 


CHAPTER  XXI 
FISHES  AND  FISHERIES 

With  this  chapter  we  begin  the  discussion  of  the  last  and 
highest  branch  of  the  animals.  The  branch  is  more  commonly 
known  as  the  vertebrates,  because  all  except  a  few  of  the  lower 
forms  in  it  possess  a  backbone  made  up  of  a  number  of  sepa- 
rate vertebrae.  This  character  separates  them  from  all  the 
other  animals  that  we  have  studied.  Those  forms  that  do 
not  have  a  vertebral  column  have,  in  common  with  the 
vertebrate  forms,  in  some  stage  of  their  development,  apeculiar 
structure  called  the  noiochord,  which  consists  of  a  series  or  cord 
of  cells  extending  longitudinally  through  the  body  just  below 
the  spinal  nerve-cord.  The  presence  of  this  notochord  and 
of  gills  in  the  neck  region  are  about  the  only  claims  some  of 
the  members  of  the  branch  have  to  be  classed  with  the  verte- 
brates, and  it  is  on  account  of  the  notochord  that  the  name 
Chordata  has  been  given  to  the  branch. 

The  branch  is  divided  into  nine  classes  of  which  the  members 
of  five  are  familiar  while  those  of  the  other  four  are  strange 
small  marine  animals  not  at  all  popularly  known.  In  the 
class  Adelochorda  (Gr.  adelos,  concealed;  chorde,  cord)  which 
includes  the  worm-like  Balanoglossus,  the  notochord  is  im- 
perfectly developed  and  for  this  reason  some  zoologists  do  not 
consider  it  as  belonging  to  the  Chordata.  These  animals 
occur  only  in  certain  places  in  the  sea  and  are  of  particular 
interest  only  to  special  students  or  investigators.  In  the 
class  Urochorda  (Gr.  oura,  tail;  chorde,  cord),  of  which  the 
ascidians,  or  sea-squirts,  are  common  examples,  the  notochord 
is  present  only  in  the  larval  stage.  The  ascidians  when  born 
are  free-swimming  tadpole-like  creatures  with  a  short  noto- 
chord and  a  fairly  well-developed  nervous  and  digestive 
system,  eyes  and  auditory  organs.  These  larvae  soon  attach 

23? 


238    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

themselves  to  a  rock  or  some  other  firm  substance,  and  all  of 
their  organs  become  very  much  reduced  and  simplified.  The 
adult  ascidian  is  a  degenerate,  sac-like  organism  looking  as 
much  like  a  plant  as  an  animal,  and  showing  in  no  way  the 
relation  to  the  vertebrates  that  is  suggested  by  the  larva. 

As  these  two  classes  are  so  unlike  each  other  and  so  different 
from  the  vertebrates  they  are  often  considered  as  two  distinct 
subbranches  of  the  Chordata  and  all  the  other  classes  are 
included  in  a  third  subbranch,  the  Vertebrata.  In  almost  all 


FIG.  in. — An    ascidian    or    sea-squirt    from   the   coast   of    California. 
(After  Jordan  and  Kellogg.) 


of  the  Vertebrata,  the  notochord,  which  is  present  in  the  early 
stages  of  development,  is  replaced,  in  the  later  stages,  by  a 
cartilaginous  or  bony  backbone  or  spinal  column. 

The  class  Leptocardii  (Gr.  leptos,  small ;  kardia,  heart)  includes 
the  primitive  lancelet,  in  which  the  notochord  is  persistent  and 
unsegmented.  Lancelets  occur  in  the  sand  in  shallow  water 


FISHES  AND  FISHERIES  239 

along  the  Atlantic  seacoast.  They  are  slender,  translucent 
little  creatures  of  very  lowly  organization. 

The  class  Cyclostomata  (Gr.  kyklos,  circle;  stoma,  mouth) 
includes  the  lampreys  and  hag-fish,  slender,  eel-like  forms  hav- 
ing a  sucker-like  mouth  but  no  jaws.  The  lampreys,  genus 
Petromyzon,  occur  in  both  fresh  and  salt  water,  those  living 
in  the  sea  ascending  rivers  to  spawn.  They  sometimes  attach 
themselves  to  fishes  by  their  sucker-like  mouth  and  rasp  the 
skin  and  suck  the  blood.  In  this  way  they  are  of  economic 
importance  as  they  may  thus  destroy  some  of  the  food  fishes. 
The  hag-fish  may  burrow  into  the  abdominal  cavity  of  other 
fish  and  devour  the  entire  flesh  and  viscera  in  a  short  time. 

The  other  five  classes  are  the  familiar  ones  of  the  Pisces 
(L.  piscis,  fish),  or  fishes,  Amphibia  (Gr.  amphi,  on  both  sides; 
bios,  life),  or  frogs,  toads  and  salamanders,  Reptilia  (L.  repo, 


FIG.  112. — A  lamprey,  Petromyzon  marinus.     (After  Goode.) 

to  creep),  or  turtles,  snakes  and  crocodiles,  AvesCL.  avis,  bird), 
or  birds,  and  Mammalia  (L.  mamma,  breast),  or  mammals. 
The  fishes  constitute  the  largest  class  of  vertebrate  animals, 
about  13,000  species  being  known,  3000  of  which  live  in  North 
America.  They  occur  in  almost  all  ponds,  lakes  and  streams 
and  in  the  ocean,  and  vary  in  size  from  the  great  basking  shark, 
Cetorhinus,  which  reaches  a  length  of  thirty-six  feet,  to  the  dwarf 
goby,  Mistichthys,  which  is  less  than  half  an  inch  long.  Be- 
tween these  extremes  is  found  every  variety  in  size,  form 
and  relative  proportions.  The  body  may  be  greatly  elongated 
and  almost  cylindrical  as  in  the  eels,  or  long  and  flattened 
from  side  to  side  as  in  the  ribbon-fishes,  or  globe-shaped  as 
in  the  globe-fish. 


240    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

In  habits  too  they  differ  as  much  as  in  size  and  shape. 
Some  live  only  in  quiet  ponds  or  lakes,  others  occur  in  the 
swiftest  mountain  streams;  some  live  only  in  fresh  water, 
others  in  the  brackish  waters  of  the  bays  or  the  salt  water  of 
the  sea.  Certain  kinds  live  close  to  the  surface  of  the  water, 
others  at  moderate  depths  and  still  others  in  the  deepest 
parts  of  the  ocean. 

General  Form  and  Structure. — A  typical  fish,  such  as  a  sun- 
fish  or  perch,  has  the  body  more  or  less  pointed,  the  sides 
somewhat  flattened,  the  head  wedge-shaped,  and  in  many 
other  ways  shows  a  body  formed  for  moving  rapidly  through 
the  water.  Most  fish  have  the  body  covered  with  scales,  al- 
though many  have  the  skin  naked  or  covered  with  small  scales 
so  hidden  in  the  skin  as  to  be  hardly  visible.  The  scales  are 
small  horny  or  bony  plates,  outgrowths  of  the  skin,  which 
usually  overlap  each  other  like  shingles.  The  number,  shape 
and  size  of  these  scales  are  characters  that  are  much  used  by 
ichthyologists  in  classifying  fishes.  Three  regions  of  the  body 
may  be  recognized,  the  head,  the  trunk  and  the  tail,  the  latter 
comprising  that  part  of  the  body  beyond  the  anal  opening. 
On  the  head  are  two  usually  conspicuous  eyes  set  in  protective 
sockets.  There  are  usually  no  eyelids,  the  skin  of  the  body 
being  continuous,  but  transparent,  over  the  eyes.  Fishes  are 
near-sighted  and  vision  is  probably  not  very  precise,  although 
the  trout  and  some  others  seem  to  possess  a  very  keen  eye- 
sight. In  some  of  the  deep  sea  fishes  and  in  some  cave-dwell- 
ing species  the  eyes  are  rudimentary  or  wanting. 

The  mouth  in  most  fishes  is  comparatively  large  and  trans- 
verse, and  the  jaws  usually  bear  numerous  teeth  that  enable 
the  fish  to  bite  or  hold  their  prey.  Some  fishes,  however, 
have  the  mouth  small  and  round  and  fitted  for  sucking  rather 
than  biting,  and  many  have  few  or  no  teeth. 

The  nostrils  are  paired  openings  usually  situated  in  front 
of  the  eyes.  They  end  in  a  pair  of  nasal  sacs  and  do  not 
open  into  the  roof  of  the  mouth  as  they  do  in  mammals,  and 
so  have  no  relation  to  breathing.  The  sense  of  smell  is  rela- 
tively acute  in  most  fishes.  On  each  side  of  the  head  is  a 
flap-like  gill-cover,  or  operculum,  the  posterior  margin  of  which 


swim-bladder 


nostrils 


lateral  line 


gill-rakers 

bladder      I     9\.  *  ~> 
V 
\ 


opercular  flap 
1      liver 


I    ventricle 
conus  artcrioxi'x 


Fir..    113. — Dissection 


dorsal  fa  ^        ,,  fav!ty  °f  tfie  *<>'"» - 

t,'  kidney 


^urinary  bhtddcr 
opening  from  kidneys 


body  mmcles 


jlden  sunfish. 


FISHES  AND  FISHERIES  241 

is  free  so  that  water  may  be  taken  in  at  the  mouth  and  pass 
out  through  the  gill-openings.  The  gills  consist  of  a  series 
of  slender  filaments  attached  to  bony  arches.  In  these  fila- 
ments a  supply  of  blood  is  constantly  circulating  in  fine 
capillaries  through  the  walls  of  which  carbon  dioxide  is  given 
off  and  a  fresh  supply  of  oxygen  taken  from  the  water  that  is 
flowing  over  the  gills.  In  some  of  the  sharks  and  in  some  of 
the  flat  rays  that  lie  on  the  sea-bottom  a  pair  of  spiracles  or  small 
openings  occur  behind  the  eyes.  These  open  into  the  mouth 
and  the  water  can  pass  in  through  them  instead  of  through  the 
mouth-opening.  On  the  head  of  some  fishes  are  to  be  found 
soft  pendulous  filaments,  sharp  spines,  or  other  appendages. 
On  the  trunk  usually  occur  two  pairs  of  paired  fins  and  two  or 
more  unpaired  fins. 

Just  back  of  the  gill-openings  are  the  pectoral  fins,  which 
are  homologous  with  the  fore  limbs  of  the  other  vertebrates. 
On  the  ventral  side  of  the  body  is  another  pair  of  fins,  the 
pelvic  fins,  which  correspond  to  the  hind  limbs.  The  pelvic 
fins  may  be  placed  well  forward,  almost  under  the  head,  or 
well  back  on  the  body.  The  unpaired  or  median  fins  consist 
of  the  dorsal  fin  above,  the  anal  fin  below,  and  at  the  posterior 
end  of  the  body,  the  caudal  fin,  or  tail.  Salmon  and  trout, 
and  a  few  other  fishes,  have  in  addition  to  these  a  small,  soft 
adipose  fin  between  the  dorsal  and  caudal  fins.  The  median 
fins  are  folds  of  the  skin  of  the  body  supported  by  more  or  less 
firm  rays.  The  stiff  unjointed  rays  are  known  as  spines  and 
the  others,  which  are  softer  and  made  up  of  little  joints,  are 
called  soft  rays. 

The  stiff  sharp  spines  in  the  paired  median  fins  are  often 
very  effective  weapons  of  defense  as  a  wound  made  by  them 
may  be  very  severe,  particularly  when  made  by  the  spines  with 
serrated  or  ragged  edges.  Some  of  the  scorpion-fishes  and 
others  secrete  a  poison  which  is  introduced  into  the  wound 
made  by  the  spine. 

Along  the  side  of  most  fishes,  extending  from  the  head  to 
the  caudal  fin,  is  a  series  of  modified  scales  which  mark  the 
lateral  line.  This  lateral  line  is  subject  to  considerable  varia- 
tion in  regard  to  its  position  and  structure.  In  connection 

16 


24 2    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

with  it  are  mucous  tubes  and  other  pores.  It  is  well  supplied 
with  nerves  and  it  has  been  thought  by  some  to  be  an  organ 
of  sense,  perhaps  some  sense  that  man  does  not  possess  and 
therefore  does  not  understand.  It  is  closely  associated  with 
the  ear-sac,  and  possibly  has  some  similar  function,  that  is, 
of  determining  vibration  waves. 

Most  fishes  are  colored  in  such  a  way  that  they  are  hard  to 
detect  in  their  natural  environment,  and  are  thus  protected, 
in  a  measure,  from  their  natural  enemies.  Some  show  bright 
colors  only  at  breeding  time  while  still  others  are  beautifully 
and  brilliantly  colored  at  all  times. 

The  skeleton  consists  of  the  many  bones  composing  the  skull 
and  jaws,  the  shoulder  girdle,  the  backbone  with  a  varying 
number  of  ribs  and  intermuscular  bones,  and  the  bones  sup- 
porting the  fins.  Most  of  these  bones  are  comparatively  soft 
having  little  lime  in  them.  Indeed,  in  many  cases  they  are 
mere  cartilage.  The  small  free  intermuscular  bones  lie  im- 
bedded in  the  flesh,  and  when  abundant  materially  lessen  the 
value  of  the  fish  for  food. 

The  air-bladder  or  swim-bladder  is  a  characteristic  struc- 
ture that  is  found  in  many  fishes.  In  the  garpike,  bowfin 
and  the  lung-fishes  it  is  connected  with  the  esophagus  and  is 
used  as  a  lung  for  breathing.  In  others  it  is  joined  through 
the  modified  bones  of  the  neck  to  the  organ  of  hearing.  Its 
normal  function  seems  to  be  hydrostatic,  that  is,  it  helps  to 
keep  the  fish  of  the  same  specific  gravity  as  the  water  by  the 
absorption  or  secretion  of  gas. 

Most  fishes  lay  eggs  which  are  fertilized  outside  of  the  body 
by  the  male  pouring  the  milt,  or  spermatozoa,  over  them  as 
they  settle  into  the  gravel  or  other  places  where  they  are  to 
develop.  A  few  make  more  or  less  elaborate  nests  where  the 
eggs  are  protected  until  they  hatch.  These  usually  produce 
fewer  eggs  than  those  that  make  no  provision  for  the  care  of 
their  eggs.  Some  of  the  perch-like  kinds  and  a  few  others 
retain  the  eggs  in  the  body  until  they  hatch,  and  thus  produce 
living  young. 

Fish  Culture. — Many  of  our  best  food-fishes  occur  in  seem- 
ingly inexhaustible  numbers.  When  we  read  of  shoals  of 


FISHES  AND  FISHERIES  243 

fish  extending  over  an  area  of  six  or  eight  square  miles  or  of 
their  being  so  thick  in  a  stream  that  they  completely  fill  it 
from  bank  to  bank,  or  of  their  filling  the  nets  and  traps  of 
the  fishermen  so  full  that  they  cannot  be  lifted,  we  can  hardly 
believe  that  the  time  will  come  when  the  supply  will  not  meet 
the  demand.  Yet  when  we  consider  that  we  sometimes  take 
3,000,000,000  herring,  and  more  than  455,000,000  pounds  of 
salmon,  and  75,000,000  pounds  of  white  fish  in  one  season, 
and  other  kinds  of  fish  in  corresponding  numbers,  it  seems 
evident  that  the  supply  will  not  always  last,  especially  as  by 
far  the  greatest  number  of  these  fish  are  taken  while  they 
are  on  their  way  to  their  spawning  beds  or  after  they  have  just 
reached  them.  Indeed,  many  of  our  most  profitable  fisheries 
would  have  been  ruined  long  before  this  if  the  state  and 
national  governments  had  not  come  to  their  aid,  and  by  more 
or  less  effective  laws  stopped  some  of  the  needless  slaughter, 
and,  especially,  by  artificial  propagation,  increased  the  supply. 
We  are  accustomed  to  say  that  nature's  way  of  doing  a  thing 
is  the  best  way,  but  this  is  not  always  so  by  any  means. 
When  the  female  king  salmon  leaves  the  ocean,  swims  far  up 
some  stream  and  reaches  her  spawning  bed,  she  hollows  out 
a  little  place  in  the  gravel  and  deposits  her  eggs  which 
scatter  over  the  bottom.  Many  of  them  settle  in  crev- 
ices where  they  are  safe,  but  others  are  left  exposed, 
attractive  morsels  for  the  hungry  trout  and  other  fish  which 
haunt  the  spawning  beds.  Soon  after  the  female  has  laid 
her  eggs  the  male  deposits  close  to  them  the  milt,  which  con- 
tains the  spermatozoa.  Probably  a  large  percentage  of  the 
eggs  are  fertilized.  They  remain  in  their  hiding  places  for 
about  two  months,  unless  disturbed  by  freshets.  Finally  the 
young  salmon  issues  and  after  about  two  months  more  of  wait- 
ing, during  which  time  it  is  absorbing  the  yolk  sac  which  fur- 
nishes it  its  food,  it  ventures  forth  to  seek  other  food.  Most 
of  these  young  salmon  fall  a  prey  to  the  larger  fish  and  other 
enemies  before  they  are  old  enough  to  be  able  to  take  care  of 
themselves.  Thus  from  the  thousands  of  eggs  that  are  laid 
by  the  parent  salmon  comparatively  few  young  issue  and  live 
long  enough  to  make  their  perilous  journey  back  to  the  sea. 


244    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

This  is  nature's  way,  and  it  is  a  wasteful  one,  yet  enough  fish 
were  produced  each  year  to  maintain  the  species  in  great 
numbers.  But  when  the  demand  of  man  for  fish  became  so 
great  that,  hundreds,  and  later,  thousands  of  men  devoted 
their  time  and  energies  to  catching  salmon  wherever  possible, 
it  was  found  that  the  number  of  fish  was  fast  decreasing. 
Under  these  conditions,  the  government  established  hatcheries 
along  some  of  the  rivers  where  the  salmon  naturally  spawned. 

On  these  spawning  beds  the  salmon  are  taken  by  means  of 
traps  or  nets,  and,  if  the  eggs  are  ripe,  the  body  of  the  female 
is  held  over  a  pan  and  gently  pressed  so  the  eggs  will  flow 
out  into  the  water  in  the  pan.  The  milt  from  the  male  is 
procured  in  the  same  way,  and  is  poured  over  the  eggs,  thus 
fertilizing  them.  The  eggs  are  then  taken  to  the  hatchery, 
where  they  are  placed  in  wire  baskets  which  are  lowered  into 
troughs  of  flowing  water  and  kept  until  the  young  fish  hatch 
and  have  absorbed  the  yolk  sac  and  are  able  to  take  care  of 
themselves.  In  this  way  80  per  cent,  to  95  per  cent,  of  the 
eggs  that  are  taken  are  saved,  and  millions  of  young  fish  are 
turned  into  the  streams  from  the  hatcheries  that  are  located 
along  the  tributaries  of  many  of  the  most  important 
salmon  rivers. 

This  is  surely  a  great  improvement  over  nature's  wasteful 
methods.  In  this  way  the  fisheries  on  the  Sacramento  and 
Columbia  rivers  have  been  maintained,  whereas  otherwise  they 
would  have  long  ago  been  depleted.  Other  salmon  hatcheries 
have  been  established  in  Washington,  British  Columbia  and 
Alaska,  until  now  provision  is  made  for  caring  for  the  eggs 
of  all  of  the  species  of  salmon,  especial  attention  being  paid 
to  the  king,  or  chinook,  and  the  red,  or  sockeye,  salmon,  as 
these  are  commercially  the  most  important 

In  the  same  way  the  eggs  of  many  species  of  trout  are  taken 
and  hatched,  and  the  young  turned  directly  into  streams  or 
lakes,  or  kept  in  ponds  where  they  can  be  fed  and  reared. 
At  certain  stages  of  their  development  the  eggs  can  be  packed 
and  shipped  long  distances,  or  the  young  may  be  carried  shorter 
distances  in  cans  if  the  water  is  kept  well  aerated.  Thus  many 
barren  streams  and  lakes  can  be  stocked  with  choice  varieties  of 


FISHES  AND  FISHERIES  245 

trout  or  the  supply  may  be  increased  in  the  regions  where  too 
constant  fishing  has  depleted  the  numbers. 

With  certain  modifications  of  this  general  plan,  necessitated 
by  the  structure  and  habits  of  the  fish,  the  black  and  striped 
bass,  the  whitefish,  shad,  pike,  codfish,  mackerel  and  others  are 
also  artificially  propagated  in  great  quantities. 

The  federal  government  now  operates  thirty-six  permanent 
hatcheries,  besides  nearly  a  hundred  auxilliary  stations.  In 
these  more  than  forty  species  of  the  best  food  and  game  fishes 
are  handled.  These  hatcheries  are  distributed  over  thirty- 
three  states,  and  some  of  these  states  themselves  maintain 
other  hatcheries  which  handle  even  more  fish  than  the  govern- 
ment hatcheries.  New  methods  and  improved  appliances  are 
constantly  being  adopted,  wonderfully  increasing  the  usefulness 
of  these  establishments.  In  this  way  the  United  States 
Bureau  of  Fisheries  and  the  various  State  Fish  Commissions 
are  doing  a  valuable  work  in  economic  zoology  and  one  that 
can  be  appreciated  by  all  citizens.  The  same  Bureau  and 
Commissions  are  at  work  also  on  similar  problems  in  con- 
nection with  the  lobster,  oyster,  crab,  shrimp,  clam,  mussel 
and  other  invertebrate  animals  that  are  considered  as  a  part 
of  our  fishery  resources. 

Classification. — The  class  Pisces  may  be  divided  into  four 
sub-classes,  namely:  the  Elasmobranchii,  including  the  sharks, 
skates,  torpedoes,  etc.;  iheHolocephali,  including  the chimaeras, 
a  few  strange-bodied  forms;  the  Teleostomi,  including  nearly 
all  of  the  other  fishes,  as  the  sturgeons,  catfish,  bass,  salmon, 
trout,  cod,  mackerel,  herring,  etc.;  and  theDipneusti,  or  lung- 
fishes,  represented  by  only  a  few  genera  whose  members  have 
lungs  in  addition  to  gills. 

The  Sharks,  Skates  and  Ray.  (sub-class  Elasmobranchii}. — 
These  differ  from  the  bony  fishes  in  several  important  respects, 
and  some  icthyologists  raise  the  sub-class  to  the  rank  of  a 
class.  They  have  a  skeleton  composed  of  cartilage,  there  is 
no  operculum,  and  no  true  scales.  Their  teeth  are  distinct, 
often  large  and  highly  specialized.  All  the  members  of  the 
group  are  marine. 

The  fierce,  carnivorous  and  voracious  sharks  live  in  the 


246    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

surface  waters  and  feed  on  any  other  animals  that  they  can 
capture.  The  shark's  mouth  is  on  the  underside  of  the  head, 
so  it  must  turn  over  on  its  back  in  order  to  sieze  any  prey 
that  is  swimming  above  it.  The  great  basking  sharks,  genus 
Cetorhinus,  which  reach  a  length  of  nearly  forty  feet,  often 
gather  in  numbers  and  float  motionless  on  the  surface  of  the 
sea.  The  great  white  shark,  Carcharodon  carcharias,  occurs 


FIG.  114. — The  common  skate,  Raja  erinacca.     (From  Kingsley.) 

in  all  warm  seas,  and  because  it  does  not  hesitate  to  attack 
man  it  is  often  known  as  the  man-eating  shark.  It  attains  a 
length  of  thirty  feet  or  more.  The  smooth  dogfish  shark, 
Mustelus,  the  horned  dogfish  shark,  Squalus,  and  the  sand- 
shark,  Carcharias,  often  occur  in  great  numbers  in  shallow 
waters  and  do  much  damage  by  destroying  lobsters  and  many 
valuable  food  fishes.  They  are  a  great  nuisance  on  the 


FISHES  AND  FISHERIES  247 

fishing  grounds  not  only  on  account  of  the  fact  that  they  kill 
but  because  they  drive  away  the  schools  of  fish  and  squid  and 
destroy  the  nets  and  traps. 

The  skates  and  rays  have  a  broad,  flattened  body  with  the 
gill-openings  on  the  underside.  They  are  usually  sluggish, 
lying  at  the  bottom  of  shallow  waters  along  the  shore  feeding 
on  crabs,  molluscs  and  bottom  fishes.  The  small  common 
skates,  or  "  tobacco-boxes,"  Raja  erinacea,  which  reach  a 
length  of  about  twenty  inches,  and  the  larger  "  barn-door 
skates,"  R.  Icevis,  are  numerous  along  the  Atlantic  Coast. 
The  sting-rays,  genus  Dasyatis,  which  lie  in  the  sand  in  shallow 
water,  have  a  barbed  spine  on  their  whip-like  tail  which  makes 
a  very  painful  wound.  The  torpedoes,  or  electric-rays,  have, 
on  either  side  of  the  head,  modified  bundles  of  muscles  which 
store  up  considerable  electric  energy.  The  discharge  from 
these  electric  organs  can  give  a  strong  shock  to  animals  coming 
in  contact  with  them.  It  is  said  that  a  discharge  from  a 
large  electric-ray  is  sufficient  to  disable  a  man  temporarily. 
The  saw-fish,  Pristis  pectinatus,  differs  from  the  typical  rays 
by  having  the  body  more  elongate  and  shark-like.  The  head 
is  prolonged  into  a  long  saw-like  snout  which  may  reach  a 
length  of  five  feet  or  more.  This  may  be  used  as  a  weapon  of 
defense  or  to  kill  the  small  sardines  and  herring  upon  which 
the  saw-fishes  feed. 

The  Chimaeras,  or  "Elephant  Fishes"  (sub-class  Holo- 
cephali}. — These  fishes  compose  a  small  group  of  peculiar 
forms  looking  somewhat  like  the  smaller  sharks.  Most  of  them 
live  in  deep  water,  but  others  are  rather  common  in  the 
shallow  water  of  bays  along  both  coasts  of  America  and  else- 
where. They  are  of  very  little  economic  importance. 

The  True  Fishes  (sub-class  Teleostomi}. — To  this  sub-class 
belong  nearly  all  of  our  common  fishes,  both  of  fresh  water 
and  ocean.  In  most  of  them  the  skeleton  is  bony  and  not 
cartilaginous  as  in  the  sharks  and  rays.  The  sturgeons, 
family  Acipenserida,  are  the  notable  exception  to  this  rule,  as 
their  skeleton  is  cartilaginous.  In  the  garpikes  and  a  few 
others  the  skeleton  is  only  partly  bony.  The  sturgeons  occur 
in  both  salt  and  fresh  water,  some  of  them  attaining  a  weight 


248    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

of  300  to  500  pounds  or  more.  The  skin  is  provided  with  series 
of  large  bony  plates  on  the  sides,  on  the  back  and  beneath. 
These  plates  are  not  contiguous,  and  so  do  not  form  a  complete 
covering  for  the  body.  Although  the  meat  is  rather  coarse  it  is 
largely  used  for  food,  and  the  egg  masses,  or  roe,  are  used  in 
making  caviar.  Some  of  the  largest  species,  such  as  those  that 
run  up  into  the  Columbia,  were  almost  exterminated  by  wanton 
destruction  before  the  need  of  conserving  them  was  realized. 

The  garpikes,  family  Lepisosteida,  are  common  in  the 
lakes  and  rivers  of  the  middle  and  eastern  United  States. 
They  are  long  and  slender,  and  the  body  is  covered  with  close- 
set  horny  scales  which  form  a  complete  armor.  They  are 
carnivorous  and  often  destroy  great  numbers  of  valuable  food 
fishes,  they  themselves  being  unfit  for  food. 

The  catfishes,  family  Siluridce,  are  distinguished  by  their 
smooth  skin,  which  is  without  scales,  and  by  the  somewhat 
flattened  head  and  the  numerous  long,  soft,  slender  feelers 
about  the  mouth.  There  are  many  kinds  known  by  different 
common  names,  such  as  "horned  pout,"  "bull-head,"  "chan- 
nel-cat," etc.  The  latter  sometimes  reaches  a  weight  of 
200  pounds.  Most  of  them  are  excellent  food  fishes. 

The  suckers,  family  Catostomida,  occur  abundantly  in  almost 
all  regions.  They  feed  on  insects  and  small  aquatic  animals 
which  they  suck  up  into  their  mouth.  Some  reach  a  length  of 
about  three  feet,  but  their  flesh  is  flavorless  and  full  of  bones, 
so  they  are  but  little  used  for  food. 

The  family  Cyprinidoe  includes  the  carps,  chubs,  minnows 
and  gold  fishes.  One  of  the  most  common  carps,  Cyprinus 
carpio,  commonly  known  as  the  European  carp,  is  a  native  of 
China,  where  it  has  been  domesticated  for  centuries.  About 
300  years  ago  it  was  introduced  into  Europe  and  later  into 
the  United  States  where  its  cultivation  has  attracted  consider- 
able attention.  They  are  not  generally  prized  as  food  fish 
by  Americans,  but  are  largely  used  by  other  nationalities  and 
so  are  important  fish  in  many  of  the  larger  markets.  The 
chubs  (Notropis  spp.)  are  abundant  in  nearly  all  fresh  water, 
and  sometimes  reach  considerable  size,  but  they  are  of  little 
value  as  food.  Many  of  the  smaller  species  belonging  to  this 


FISHES  AND  FISHERIES  249 

family  are  known  as  minnows.  They  are  an  important  source 
of  food  for  larger  fish,  and  are  much  used  for  bait. 

The  goldfish,  Carassius  auratus,  is  a  native  of  China.  In 
its  native  waters  or  where  it  escapes  from  domestication  it  is 
of  a  greenish  hue,  the  beautiful  golden  yellow  color  being 
brought  about  and  retained  by  artificial  selection.  In  the 
same  way  the  many  strange  shapes  and  varieties  have  been 
produced. 

The  true  eels,  family  Anguillida,  are  long,  slender  and  with 
small  inconspicuous  scales.  They  are  found  in  most  fresh 
water  streams  and  lakes  where  they  feed  chiefly  on  all  kinds 
of  refuse,  but  they  frequently  destroy  great  numbers  of  shad, 
herring  and  other  fish,  particularly  at  spawning  time.  They 
go  down  the  rivers  to  the  sea  to  spawn.  The  ova  are  very 
minute,  and  it  has  been  estimated  that  a  single  female  may 
produce  over  10,000,000  eggs.  They  are  regarded  as  excellent 
food  fishes. 

The  conger-eels,  family  Leptocephalida,  are  scaleless,  occur 
in  the  sea  at  moderate  depths,  and  are  little  used  as  food  in 
America. 

The  family  Clupeidce  includes  the  herring,  sardines,  shad, 
menhaden  and  others.  The  herring,  genus  Clupea,  occur  in 
both  the  Atlantic  and  Pacific,  and  when  they  come  in  shore  at 
spawning  time  they  are  taken  in  great  numbers  and  canned  as 
sardines,  dried,  smoked  or  salted,  or  used  fresh  for  food  or  bait. 
The  herring  fisheries  of  the  North  Atlantic  are  particularly 
important.  It  has  been  estimated  that  at  least  10,000,000,000 
herring  are  taken  by  British  and  American  fisherman  each  year 
representing  a  weight  of  more  than  one-third  as  many  pounds. 
They  occur  in  great  shoals  sometimes  miles  in  extent. 

The  sardines  (genus  Sardinella)  are  fine-flavored  little  fish 
with  rather  soft  bones.  Preserved  in  oil  they  form  a  most 
important  article  of  commerce.  Great  numbers  are  used  for 
bait. 

The  shad  (genus  Alosa),  although  very  bony,  are  highly 
esteemed  on  account  of  their  fine  delicate  flavor.  They  occur 
on  both  coasts,  having  been  introduced  into  California,  and 
ascend  the  rivers  to  spawn  in  May.  They  are  very  prolific, 


250    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

each  female  yielding  usually  about  30,000  eggs,  but  some  have 
been  known  to  produce  two  or  three  or  even  five  times  as  many. 

Although  the  menhaden  (genus  Brevoortia)  are  but  little 
valued  for  food,  they  are  of  great  commercial  importance 
on  account  of  the  oil  that  is  extracted  from  them.  The  refuse 
is  used  for  fertilizer.  They  are  also  largely  used  in  the  prepa- 
ration of  fish  meal  for  domestic  animals. 

The  anchovies,  family  Engraulidce,  are  fine-flavored  oily 
little  fish  that  are  often  preserved  in  oil  or  spices.  They  are 
very  abundant  in  many  waters,  and  form  an  important  source 
of  bait  and  of  food  for  other  fishes. 

In  many  respects  the  family  Salmonida,  including  the  salmon, 
trout,  and  whitefish,  is  the  most  important  of  all.  The 
salmon  fisheries  constitute  one  of  the  principal  industries  of 
the  Pacific  northwest,  the  whitefish  are  among  the  most 
important  fish  of  the  Lake  regions,  and  the  trout  are  found 
in  almost  all  swift-flowing  streams  and  clear  cold  lakes,  and 
are  more  sought  after  by  the  angler  than  any  other  fish. 

The  Pacific  salmon,  genus  Oncorhynchus,  occur  in  the  north 
Pacific.  Little  is  known  of  their  habits  while  in  the  sea, 
but  just  before  spawning  time  they  enter  certain  rivers  and 
start  upstream  for  the  spawning  grounds,  taking  no  food 
while  in  fresh  water.  The  king  salmon,  or  quinnat  salmon, 
enters,  in  enormous  numbers,  such  rivers  as  the  Sacramento, 
Columbia,  Frazer  and  Yukon,  large  streams  fed  by  mountain 
snows.  Up  these  rivers  they  may  make  their  way  through 
rapids  and  over  falls  for  several  hundred  miles,  often  to  the 
very  head  waters,  before  spawning.  In  the  Yukon  they  may 
ascend  2250  miles  from  the  ocean. 

The  red  salmon,  or  sock  eye  salmon,  is  commercially  the  most 
important  of  all.  They  are  taken  in  large  seines  or  traps  in 
Puget  Sound  or  similar  bays  while  going  in  great  schools  to 
the  rivers  which  they  ascend  to  reach  their  spawning  grounds. 
They  will  enter  only  such  rivers  as  are  fed  by  lakes,  and  spawn 
in  the  small  streams  that  flow  into  the  lakes,  sometimes  1000 
to  1800  miles  from  the  ocean.  The  other  species  spawn  closer 
to  the  sea  in  almost  any  fresh  water  stream.  After  spawning, 
the  salmon  remain  near  their  eggs  until,  too  weak  to  resist 


FISHES  AND  FISHERIES 


251 


the  current,  they  drift  down  and  die.  Most  of  the  young 
make  their  way  to  the  sea  and  a  few  return,  three  or  four 
years  later,  as  mature  fish  ready  to  spawn.  The  salmon 
fisheries  have  long  been  one  of  the  most  important  industries 
on  the  Pacific  Coast.  In  some  years  more  than  5,000,000 
cases  are  packed,  each  case  containing  forty-eight  one-pound 
cans.  The  value  of  such  a  pack  is  more  than  $25,000,000. 

The  Atlantic  Coast  salmon,  Salmo  salar,  ascend  fresh  water 
streams  to  spawn,  but  unlike  the  western  salmon,  they  return 
alive  to  the  sea  again. 

There  are  many  species  of  trout,  as  the  black- spotted, 
rainbow  and  cut-throat,  belonging  to  the  genus  Salmo.  Many 


FIG.  115. — The  rainbow-trout,  Salmo  irideus. 

of  these  species  are  represented  by  one  or  more  varieties,  so  it 
is  often  difficult  for  even  an  expert  ichthyologist  to  determine 
the  species  definitely.  There  are  certain  well-marked  types, 
however,  and  each  region  has  its  particular  representative  trout 
type  which  affords  the  best  kind  of  sport  to  the  enthusiastic 
anglers.  The  genus  Sahelinus  includes  some  of  the  choicest 
and  most  beautiful  of  the  brook  trout.  They  are  frequently 
called  char,  and  differ  from  the  members  of  the  genus  Salmo 
in  that  the  body  is  covered  with  round  crimson  or  gray  spots 
which  are  paler  than  the  ground  color.  The  scales  are  smaller 
and  so  imbeded  in  the  skin  as  generally  to  escape  notice. 

The  whitefish,  genus  Coregonus,  occurring  usually  in  clear 
cold  lakes  or  streams,  are  regarded  as  especially  fine  food 


252    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

fishes.  The  largest  of  the  species  of  this  genus  ranges  from 
New  York  and  the  Great  Lakes  northward.  The  whitefish 
constitute  the  most  imporant  group  of  the  fresh  water  fishes. 
While  the  average  weight  is  probably  under  four  pounds  some 
attain  a  weight  of  more  than  twenty  pounds.  Although 
considerable  quantities  are  salted  the  largest  part  of  the  catch, 
valued  some  years  at  more  than  $1,500,000,  is  used  fresh. 

The  lake  herring,  genus  Argyrosomus,  are  closely  related  to 
the  whitefish,  but  are  not  as  highly  valued  as  food.  They 
occur  in  enormous  numbers  throughout  the  Great  Lake  region. 

The  grayling,  family  Thymallidce,  beautiful,  trout-like 
fish,  found  in  some  of  our  northern  streams  and  common  in 
Europe,  are  characterized  by  the  greatly  developed  dorsal 
fin.  They  are  superior  food  and  game  fishes. 

The  smelt,  family  Argentinida,  are  also  closely  related  to  the 
Salmonida.  They  are  mostly  marine,  and  all  are  excellent 
food  fishes.  The  eulachon,  or  candle-fish,  is  regarded  by  many 
as  the  most  delicate  and  luscious  of  all  fishes.  They  are  very 
oily  and  it  is  said  that  when  dried  and  provided  with  a  wick 
they  will  burn  like  a  candle.  The  oil  is  pressed  out  and 
used  to  some  extent  as  a  substitute  for  cod-liver  oil. 

The  pike,  family  Esocida,  are  long,  slender,  swift-swimming 
fish  found  in  many  fresh  water  lakes  and  streams,  the  fine 
muskallunge  of  the  Great  Lake  region  reaching  a  weight  of 
sixty  to  eighty  pounds.  The  smaller  pike  are  sometimes  called 
pickerel.  They  are  all  excellent  food  and  game  fishes. 

The  mullets,  family  Mugilidce,  are  found  in  both  fresh  and 
salt  water,  where  they  feed  on  the  organic  matter  that  they 
can  sift  out  of  the  mud.  In  some  regions  they  are  especially 
abundant,  particularly  along  the  Florida  and  Gulf  coast  where 
they  are  important  food  fishes. 

The  mackerel,  family  Scombrida,  are  among  the  most  im- 
portant fishes  of  the  Atlantic.  Along  the  New  England  coast 
many  villages  are  almost  wholly  dependent  upon  the  success 
attained  by  the  crews  of  the  fleets  of  splendid  mackerel 
schooners  that  each  season  put  out  to  fish.  Hundreds  of 
thousands  of  barrels  of  mackerel  are  salted  each  year,  and  great 
quantities  are  used  fresh.  Several  species  occur  along  the 


FISHES  AND  FISHERIES  253 

Atlantic  and  Pacific  Coasts  and  in  many  other  parts  of  the 
world.  Some  of  the  species  such  as  the  Spanish  mackerel  and 
the  tuna,  are  unexcelled  as  food  or  game  fishes. 

The  large  family  CentrarchidcB  includes  the  sunfishes  and 
rock  bass,  black  bass  and  others.  The  various  species  of  sun- 
fishes  occur  in  almost  all  parts  of  the  country.  Some  of  them 
are  handsomely  marked  and  they  are  all  good  food  fishes. 
The  black  bass  are  among  the  most  important  of  the  game 
fishes,  and  are  fast  taking  the  place  of  the  trout  in  many 
streams  where  the  latter  have  not  been  able  to  hold  their  own 
on  account  of  the  changed  conditions  of  the  water  and  the 
intensive  fishing.  The  bass  quickly  adapt  themselves  to  their 
surroundings  and  have  been  successfully  introduced  into 
California,  Europe  and  other  places  where  they  do  not  occur 
naturally.  The  fresh  water  white  bass  and  yellow  bass,  and 
the  larger  striped  bass  or  rock-fish  which  lives  in  the  sea  and 
runs  up  the  rivers  to  spawn,  and  many  other  important  sea 
bass,  belong  to  the  family  Serranida.  The  giant  bass,  some- 
times called  jewfish,  reaches  a  weight  of  more  than  500  pounds. 

The  family  Percidce  includes  the  wall-eyed  pike  and  the  true 
perches  of  which  the  yellow  perch  is  our  most  common  ex- 
ample. They  are  both  good  game  and  food  fishes. 

On  the  west  coast  is  a  family  of  perch-like  ocean  fishes, 
family  Embiotocida,  commonly  called  perch  or  surf- fish. 
These  differ  from  almost  all  of  the  other  higher  fish  in  being 
viviparous,  the  young  being  carried  in  the  body  of  the  mother 
until  they  have  attained  considerable  size. 

The  codfish,  family  Gadida,  is  one  of  the  most  important 
of  the  North  Atlantic  fishes.  It  occurs  also  in  the  North 
Pacific  but  in  small  numbers.  The  codfish  industry  gives 
employment  to  thousands  of  men  and  warrants  a  profitable 
investment  in  boats  and  other  apparatus  to  the  extent  of 
millions  of  dollars.  The  flesh  of  the  cod  is  flaky  and  with 
little  flavor  but  it  is  well  adapted  to  drying  or  salting  and  it 
is  in  this  condition  that  it  is  most  largely  used. 

Among  the  most  remarkable  of  our  well-known  fishes  are 
the  flounders  and  halibut,  family  Pleuronedidte.  The  young 
at  first  swim  upright  in  the  water  like  other  fishes  and  have 


254    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

their  eyes  in  the  normal  position.  But  soon  they  begin  to  rest 
on  the  bottom  and  the  eye  on  the  lower  side  begins  to 
migrate,  so  that  in  a  little  while  both  eyes  are  close  together 
on  the  upper  side  of  the  head.  Many  species  of  flounders 
and  soles  are  found  along  the  shores  of  both  oceans.  They 
are  largely  used  as  food.  The  halibut  occur  on  offshore  banks 
in  the  northern  part  of  the  Atlantic  and  Pacific  oceans.  They 
reach  a  length  of  six  to  eight  feet  and  a  weight  of  500  pounds  or 
more.  The  halibut  fisheries  are  very  important,  especially  in 
the  north  Pacific.  The  young  halibut,  called  "chicken 
halibut,"  are  tender  and  of  fine  flavor,  differing  in  this 


FIG.  1 1 6. — The  winter  flounder,  Pseudoplenronectes  americanus.     (After 

Goode.) 

respect  from  most  of  the  flat  fishes  which,  although  in  great 
demand  for  food,  do  not  have  much  flavor. 

With  this  brief  review  of  only  a  few  of  the  more  important 
of  the  many  hundreds  of  common  food  or  game  fishes  we  must 
leave  the  discussion  of  this  sub-class  without  even  a  reference 
to  the  many  strange  and  interesting  fishes  that  occur  in  the 
fresh  waters  of  other  lands  and  in  other  seas.  Among  the  coral 
reefs  that  surround  many  of  the  tropical  islands  are  to  be  found 
most  beautifully  colored  fishes;  in  the  greatest  depths  of  the 
ocean  are  strange  uncanny  fish,  some  of  which  are  provided 
with  phosphorescent  patches  on  their  heads  or  on  appendages, 
enabling  them  to  see  in  the  dark  abysses.  For  the  study  of  these 


FISHES  AND  FISHERIES  255 

and  such  others,  as  the  curious  sea-horses  and  the  remarkable 
flying-fish,  and  the  fishes  that  leave  the  water  and  wander 
over  the  land,  the  student  must  go  to  some  of  the  detailed 
works  on  fishes,  as  Jordan's  "Guide  to  the  Study  of  Fishes." 
Jordan  &  Evermann's  "American  Food  and  Game  Fishes" 
is  a  most  excellent  treatise,  popular  enough  so  that  anyone  may 
enjoy  reading  it. 

The  Lung-fishes  (sub-class  Dipneusti}. — This  sub-class, 
formerly  called  Dipnoi,  is  represented  by  only  a  few  living 
species,  occurring  in  Australia,  South  America  and  Africa. 
They  are  of  particular  interest  to  the  naturalist  not  only  be- 
cause they  are  the  sole  survivors  of  a  once  numerous  group  of 
fishes,  but  because  several  things  about  their  structure  seem 
to 'indicate  that  they  must  be  closely  allied  to  the  ancestral 
type  from  which  both  the  bony  fishes  and  the  Amphibia,  or 
frogs,  salamanders,  etc.,  have  descended.  The  gills  in  most 
of  them  remain  functional  and  are  used  while  the  animals  are 
in  the  water,  but  at  other  times,  when  they  burrow  into  the 
wet  mud  or  elsewhere,  they  breathe  by  means  of  lungs,  which 
are  spongy  sacs,  represented  in  most  fishes  by  the  air  bladder. 
The  paired  fins,  too,  have  an  elongated  jointed  axis  with  rays 
which  resemble  the  limbs  of  some  of  the  Amphibia  as  much 
as  the  fins  of  fish. 


CHAPTER  XXII 
TOADS,  FROGS  AND  SALAMANDERS 

The  toads  and  frogs  are  the  most  common  representatives 
of  the  class  Amphibia,  but  the  salamanders,  or  water-dogs, 
are  very  often  found  along  streams  or  in  moist  places.  The 
coecilians,  legless,  worm-like  or  snake-like  creatures  occurring 
in  the  tropics,  also  belong  to  this  class. 

Almost  fifteen  hundred  living  species  of  amphibians  are 
known.  These  may  be  grouped  into  three  fairly  well-defined 
orders,  the  Apoda,  or  footless,  snake-like  forms,  the  Urodela, 
or  tailed  amphibians,  and  the  Anura,  or  tailless  forms  like  the 
toad  and  frog. 

The  Coecilians  (order  Apoda). — This  order  includes  a  few 
worm-like  or  snake-like  footless  species  called  ccecilians  usu- 
ally having  small  scales  embedded  in  the  skin.  They  occur 
only  in  tropical  regions  and  are  of  no  economic  importance. 

The  Water-dogs  (order  Urodela). — 'Several  widely  different 
forms  are  grouped  together  in  this  order  so  that  it  is  often 
divided  into  suborders.  They  all  agree  in  having  a  tail,  which 
may  be  longer  or  shorter  than  the  rest  of  the  body.  The  mud- 
puppies  or  water-dogs,  genus  Necturus,  occur  in  the  rivers  and 
lakes  of  the  northern  United  States.  They  attain  a  length  of 
about  two  feet  when  full  grown.  They  have  four  legs,  and 
breathe  by  means  of  bushy  gills  which  arise  from  in  front  of 
the  forelegs.  The  sirens  or  mud-eels,  genus  Siren,  burrow  in 
the  mud  in  ponds  and  ditches  in  the  southern  states,  attaining 
a  length  of  about  three  feet.  They  have  three  pairs  of  gills 
and  only  one  pair  of  legs. 

The  large,  heavy-bodied,  blackish  water-dog  or  hell-bender, 
genus  Cryptobranchus,  is  another  aquatic  form,  but  the  ex- 
ternal gills  are  replaced  by  small  openings  or  gill  slits  which 
lead  into  the  throat.  It  is  found  along  the  Ohio  river 

256 


TOADS,  FROGS  AND  SALAMANDERS          257 

and  its  tributaries.  The  salamanders  and  newts  are  common 
in  many  regions.  Most  of  them  possess  neither  gills  nor 
gill  openings  in  the  adult.  Some  of  them  are  often  called 
lizards,  but  they  differ  widely  from  the  lizards  in  many  re- 
spects. The  body  is  soft  and  not  provided  with  scales,  and  in 
their  development  they  pass  through  a  tadpole  stage  similar 
to  that  of  the  frogs  and  toads.  Amblystoma  tigrimim  is  an 
interesting  and  widely  distributed  common  species.  In 
some  regions  the  larval  form,  known  as  axolotl,  reaches 
a  large  size  and  produces  young  before  completing  the 
usual  metamorphosis. 


FIG.  117. — A  brown  salamander,  N oto phthalmus  torosus.     (Reduced.) 

The  Frogs  and  Toads  (order  Anura). — This  is  by  far  the 
largest  and  most  important  order  of  Amphibia.  There  are 
about  a  dozen  species  of  frogs,  family  Ranidce,  found  in  the 
United  States.  The:  well  known  bullfrog,  Rana  catesbiana, 
is  the  largest  of  these,  attaining  a  length  of  seven  or  eight 
inches.  It  occurs  in:ponds  and  sluggish  streams  all  over  the 
eastern  United  States  and  in  the  Mississippi.  Valley.  Frogs 
are  very -commonly  used  as  food  in  the  United  States  but  not 
as  extensively  as  in  some  of  the  European  countries.  The  large 
hind  legs  and  "saddle"  afford  a  considerable  mass  of  very  deli- 
cately flavored  meat.  It  has  been  pointed  out  that  there  is  an 
opportunity  for  the.  development  of  a  small  but  profitable 
industry  in  raising  frogs  for  market  in  some  of  the  extensive 


258    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

areas  of  marsh  land  where  frogs  abound.  Frogs  are  used  more 
than  any  other  vertebrate  in  the  laboratories  of  schools  and 
colleges,  not  only  because  they  are  easily  obtained  but  because 
in  their  structure  and  habits  one  may  find  illustrations  of  so 
many  of  the  fundamental  facts  of  zoology.  The  tree-frogs  or 
tree-toads,  family  Hylidce,  are  more  closely  related  to  the 
toads  than  to  the  frogs.  Their  toes  are  usually  provided  with 
adhesive  disks  which  enable  them  to  cling  to  the  trunk  of  a 
tree  or  other  perpendicular  surfaces.  Their  vocal  sacs  are 


FIG.  118. — A  western  garden  toad,  Bufo  halophilus.     (Reduced.) 

large,  and  they  make  a  noise  out  of  all  proportion  to  their 
size.  Hyla  versicolor,  the  most  common  of  these  tree-frogs, 
is  green,  gray  or  brown  above,  and  has  the  power  of  slowly 
changing  from  one  color  to  another  so  as  to  produce  a  re- 
markable harmony  between  the  frog  and  its  surroundings, 
thus  making  it  almost  invisible  to  its  enemies.  This  change 
in  color  is  brought  about  by  the  expansion  or  contraction  of 
certain  pigment  cells  in  the  skin. 

The  structure  and  habits  of  the  toads,  family  Bufonida, 
have  already  been  discussed  (Chapter  II).  There  are 
about  fifteen  species  in  the  United  States  and  less  than  one 
hundred  species  in  other  lands.  Some  of  the  exotic  species 


TOADS,  FROGS  AND  SALAMANDERS          259 

are  interesting  on  account  of  the  unusual  method  of  caring 
for  their  eggs  or  young.  The  females  of  some  species  carry 
the  eggs  on  their  back  until  they  hatch.  Others  are  provided 
with  a  large  pouch  in  which  all  the  eggs  are  stored,  or  with  a 
cell-like  pouch  for  each  egg  where  the  larva  hatches  and  re- 
mains until  it  has  passed  through  the  tadpole  stage.  In  still 
other  species  the  male  cares  for  the  eggs.  All  toads  are 
beneficial  because  they  eat  so  many  noxious  insects. 

The  Frog  Book,  by  Mary  Dickerson,  gives  an  admirable 
account  of  the  kinds,  distribution  and  habits  of  the  American 
frogs  and  toads.  It  is  well  illustrated  in  color. 


CHAPTER  XXIII 
SNAKES,  LIZARDS,  TURTLES,  AND  CROCODILES 

The  large  class,  Reptilia,  including  the  turtles  and  tortoises, 
crocodiles  and  alligators,  lizards  and  snakes,  is  composed  of 
animals  differing  in  general  appearance  but  possessing  many 
characteristic  features  that  show  their  close  relationship.  Most 
of  them  are  terrestrial  in  habitat.  All  are  cold  blooded  and 
almost  all  breathe  by  means  of  lungs,  those  that  spend  part  of 
their  life  in  water  coming  to  the  surface  to  breathe.  Nearly  all 
creep  or  crawl,  dragging  the  body  on  the  ground  or  close  to  it. 
The  body  is  covered  with  scales  or  with  large  plates.  The  rep- 
tiles pass  through  no  metamorphosis  during  their  develop- 
ment, the  young  when  born  or  hatched  from  the  egg  resem- 
bling the  adult  except  in  size.  Most  reptiles  lay  eggs,  as  do 
the  birds,  and  so  are  called  oviparous.  But  the  common 
garter-snakes  and  some  other  species,  retain  the  eggs  within 
the  body  until  they  are  hatched,  and  so  are  said  to  be 
ovoviparous.  The  eggs  are  usually  laid  in  the  earth  or  sand 
or  in  vegetable  mould  and  given  no  further  care  by  the 
mother,  but  some  species  show  great  solicitude  for  the 
eggs,  guarding  them  jealously  until  they  hatch. 

In  general  appearance  some  of  the  lizards  resemble  the 
salamanders  and  other  amphibians  more  than  they  do  other 
members  of  their  own  class,  and  the  reptiles  are  usually  closely 
associated  in  the  common  mind  with  the  amphibians.  A  study 
.of  their  body  structure,  however,  shows  that  they  are  really 
more  closely  related  to  the  birds  than  to  the  amphibians.  In 
some  of  the  extinct  orders  of  reptiles  the  resemblance  to  birds 
was  quite  remarkable  from  the  fact  that  their  whole  body  was 
modified  to  fit  them  for  flight.  Some  of  these  flying  reptiles, 
the  Pterosauria,  attained  a  great  size,  having  a  wing  expanse 
of  twenty  feet,  But  that  was  during  the  Cretaceous  epoch,  or 

260 


Age  of  Reptiles,  when  the  giant  Dinosaurians,  some  of  which 
measured  over  a  hundred  feet  in  length,  roamed  the  swamps, 
and  the  whale-like  Ichthyosaurians  swam  in  the  seas. 

In  reptiles,  as  in  amphibians,  the  chief  variations  in  the  body 
skeleton  are  correlated  with  differences  in  external  body 
form.  In  the  short  compact  body  of  the  turtles  and  tortoises 
the  number  of  vertebrae  is  much  smaller  than  in  snakes. 
Some  turtles  have  only  34  vertebrae;  certain  snakes  as  many  as 
400.  The  reptilian  skull,  in  the  number  and  disposition  of 
its  parts  and  in  the  manner  of  its  attachment  to  the  spinal 
column,  resembles  that  of  the  birds,  although  the  cranial  bones 
remain  separate,  not  fusing  as  in  birds.  All  of  the  reptiles, 
except  the  turtles,  are  provided  with  small  teeth  which  serve, 
generally,  for  seizing  or  holding  prey  and  not  for  mastication. 

Reptiles  breathe  solely  by  lungs,  of  which  there  is  a  pair. 
They  are  simple  and  sac-like,  the  left  lung  being  often  much 
smaller  than  the  other.  In  turtles  and  crocodiles  the  lungs 
are  divided  internally  by  septa  into  a  number  of  chambers. 
Because  of  the  rigidity  of  the  carapace,  or  "box",  of  turtles  the 
air  cannot  be  taken  in  the  ordinary  way  by  the  use  of  the 
ribs  and  rib  muscles,  but  has  to  be  swallowed.  The  reptilian 
heart  consists  of  two  distinct  auricles  and  of  two  ventricles, 
which  in  most  reptiles  are  only  incompletely  divided,  the 
division  into  right  and  left  ventricles  being  complete  only 
among  the  crocodiles  and  alligators,  the  most  highly  organized 
of  living  reptiles. 

The  organs  of  the  nervous  system  reach  a  considerable  de- 
gree of  development  in  the  animals  of  this  class.  The  brain 
in  size  and  complexity  is  plainly  superior  to  the  amphibian 
brain  and  resembles  quite  closely  that  of  birds.  Of  the  organs 
of  special  sense  those  of  touch  are  limited  to  special  papillae 
in  the  skin  of  certain  snakes  and  many  lizards.  Taste  seems 
to  be  little  developed,  but  olfactory  organs  of  considerable 
complexity  are  present  in  most  forms,  and  consist  of  a  pair 
of  nostrils  with  olfactory  folds  on  their  inner  surfaces.  The 
ears  vary  much  in  degree  of  organization,  crocodiles  and 
alligators  being  the  only  reptiles  with  a  well-defined  outer 
ear.  This  consists  of  a  dermal  flap  covering  a  tympanum. 


262    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Eyes  are  always  present  and  are  highly  developed.  They 
resemble  the  eyes  of  birds  in  many  particulars.  All  reptiles, 
except  the  snakes  and  a  few  lizards,  have  movable  eyelids, 
including  a  nictitating  membrane  like  that  of  the  birds. 
With  the  snake  the  eye  is  protected  by  the  outer  skin,  a 
transparent  portion  of  which  remains  intact  over  the  eye. 
Turtles  and  lizards  have  a  ring  of  bony  plates  surrounding  the 
eyes  similar  to  that  of  birds.  In  addition  to  the  usual  eye 
there  is  in  many  lizards  a  remarkable  eye-like  organ,  the  so- 
called  pineal  eye,  which  is  situated  in  the  roof  of  the  cranium, 
and  is  believed  to  be  the  vestige  of  a  true  third  eye,  which  in 
ancient  reptiles  was  probably  a  well-developed  organ. 

Classification. — The  living  reptiles  may  be  divided  into  four 
orders.  One  of  these,  the  order  Rhynchocephalia,  includes  only 
a  single  lizard-like  genus  confined  to  New  Zealand.  The 
Chelonia,  including  the  turtles  and  tortoises,  are  distinguished 
by  the  scaly,  bony  or  leathery  shell  covering  the  body.  The 
Crocodilia,  or  crocodiles  and  alligators,  have  the  body  covered 
with  rows  of  sculptured  horny  scutes  or  scales,  while  the 
lizards  and  snakes,  order  Squamata,  are  usually  covered  with 
many  small,  flat,  horny,  epidermal  scales. 

Turtles  and  Tortoises. — The  short  stout  body  of  these 
animals  is  enclosed  in  a  more  or  less  firm  shell,  which  consists 
of  an  upper  portion,  the  carapace,  that  is  firmly  joined  along 
the  sides  to  the  lower  portion,  the  plastron.  From  the  front 
opening  of  this  box-like  covering  the  head  and  forelegs  may 
be  protruded  when  the  animal  is  feeding  or  moving  about, 
the  hind  legs  and  tail  being  extended  from  the  opening  along 
the  posterior  margin.  When  the  appendages  are  withdrawn 
they  fit  snugly  into  these  openings  and  the  whole  animal  is 
comparatively  safe  from  its  enemies.  In  some  turtles  the 
shell  does  not  become  hard  and  horny,  but  remains  soft  or 
leathery.  The  head  usually  terminates  in  a  hooked  beak  and 
serves  as  a  formidable  weapon  of  offense  or  defense.  Many 
of  the  turtles  are  wholly  aquatic,  feeding  on  fish,  frogs,  worms, 
molluscs  and  sometimes  small  water-fowl  or  upon  the  grasses 
that  grow  in  the  water.  Others  spend  a  part  of  their  time  on 
the  land  and  part  in  the  water  while  still  others  are  wholly 


SNAKES,  LIZARDS,  TURTLES,  AND  CROCODILES  263 

terrestrial.  The  term  turtle  is  usually  applied  to  the  aquatic 
forms,  while  the  land  forms  are  commonly  known  as  tortoises. 
The  name  terrapin  is  applied  to  some  of  the  kinds  that  are  used 
for  food.  They  all  lay  eggs,  which  may  be  deposited  in  the 
banks  of  the  ponds,  rivers  or  streams,  or  in  the  sand,  where 
they  are  incubated  by  the  sun's  rays. 

Turtles,  tortoises  and  terrapins  are  of  considerable  economic 
importance  as  some  of  them  are  highly  valued  for  food.  Also 
the  horny  carapace  of  many  species  is  very  valuable,  being 


FIG.  119. — -The  giant  land-tortoise  of  the  Galapagos  Islands,  Testudo  sp. 
(These  tortoises  reach  a  length  of  four  feet;  after  Coleman.) 

used  extensively  in  the  manufacture  of  combs  and  various 
ornaments.  Among  the  common  aquatic  species  found  in 
the  United  States  are  the  soft-shelled  turtles,  genus  Trionyx. 
The  flat  leathery  shell  as  well  as  the  enclosed  body  are  used  for 
food.  The  animal  defends  itself  viciously  when  attacked. 
The  large  snapping-turtle,  Chelydra  serpentina,  that  is  found  in 
so  many  of  the  streams  and  ponds  east  of  the  Rocky  Mountains, 
defends  itself  principally  by  its  powerful  beak  as  its  shell  is  too 
small  to  protect  it  completely.  The  southern  alligator  snap- 
ping-turtle,  Macrochelys  lacerlina,  often  attains  a  weight  of 


264    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

more  than  100  pounds.  It  is  largely  used  for  food.  Care  has 
to  be  exercised  in  handling  live  specimens  for  they  are  of  ugly 
temper  and  bite  severely. 

The  painted  turtle  or  painted  terrapin,  Chrysemys  picta, 
has  the  carapace  beautifully  marked  and  colored.  It  lives 
in  ponds  and  sluggish  streams,  feeding  on  aquatic  plants  and 
any  insects  or  small  animals  that  it  may  find  in  the  water. 

The  famous  diamond-back  terrapin,  M alacoclemmys  palustris, 
lives  in  the  salt  marshes  along  the  Atlantic  coast.  These 
animals,  once  very  abundant,  are  now  comparatively  rare 
because  they  have  been  so  much  hunted.  The  price  has 
rapidly  risen  from  a  few  cents  apiece  to  five  or  six  dollars. 

Still  more  highly  prized  for  food  is  the  great  green  turtle, 
Chelonia  mydas.  This  species  is  widely  distributed  in  tropical 
seas  and  occurs  as  far  north  along  the  Atlantic  Coast  as  the 
Carolinas.  It  lives  on  the  roots  of  eel  or  turtle  grass,  and  may 
attain  a  weight  of  500  pounds  or  more. 

The  hawk's-bill  turtle  or  tortoise-shell  turtle,  Chelonia 
imbricata,  is  the  source  of  the  beautiful  tortoise  shell  of  com- 
merce. Its  shell  is  made  up  of  a  series  of  shield-like  plates. 
About  eight  pounds  of  the  valuable  dorsal  shields  are  sometimes 
obtained  from  a  single  large  turtle  of  tropical  and  subtropical 
oceans. 

The  leather-back  turtle,  Sphargis  coriacea,  is  the  largest  of 
the  turtles,  attaining  a  length  of  six  to  eight  feet  and  a  weight 
of  a  thousand  pounds.  It  lives  in  tropical  and  semi-tropical 
seas,  going  on  land  only  to  deposit  its  eggs.  Both  the  fore 
and  hind  limbs  are  modified  into  broad  flippers  for  swimming. 
It  is  not  used  for  food. 

The  giant  tortoises,  genus  Testudo,  inhabiting  some  of  the 
tropical  islands,  often  weigh  as  much  as  300  pounds  and  some 
of  them  are  estimated  to  be  more  than  400  years  old. 

Alligators  and  Crocodiles.— The  skin  of  the  alligators  is 
thick  and  tough  and  covered  with  horny  scales.  The  legs  are 
well  developed,  but  the  animal  moves  clumsily  on  land.  The 
long,  laterally  compressed  tail  makes  them  powerful  swimmers. 
There  are  only  two  species  of  alligators,  one  occurring  in  China, 
the  other,  Alligator  mississippiensis,  in  the  southern  parts  of 


SNAKES,  LIZARDS,  TURTLES,  AND  CROCODILES  265 

the  United  States.  The  American  alligator  may  grow  to  be 
ten  or  twelve  feet  long,  and  is  hunted  for  its  skin  which  makes 
strong,  beautifully  marked  leather  that  takes  a  fine  polish. 
The  wholesale  slaughter  of  these  animals  for  their  skin  has 
so  greatly  reduced  their  numbers  that  extinction  is  threatened 
unless  measures  are  taken  to  protect  them  in  certain  preserves. 

The  crocodiles  are  more  widely  distributed  than  are  the 
alligators.  The  American  crocodile,  Crocodilus  americanus, 
is  found  in  Florida,  Mexico  and  South  America.  It  differs 
from  the  alligator  in  having  a  longer,  narrower  head. 

The  African  crocodile,  C.  niloticus,  is  a  ferocious  species 
often  attacking  man  and  is  greatly  feared  by  the  natives  of 
that  continent.  There  are  several  other  crocodile  kinds  in 
various  parts  of  the  world,  some  of  them  reaching  a  length  of 
twenty  feet  or  more.  The  skin  of  many  of  the  species  is 
used  for  leather. 

The  Indian  gavial,  Gamalis  gangeticus,  common  in  the 
Ganges,  attains  a  length  of  twenty  feet  or  more,  and  is  reputed 
to  feed  on  the  bodies  of  children  that  are  thrown  into  the  river 
by  the  natives.  Its  natural  food  is  fish.  It  is  distinguished 
from  the  alligators  and  crocodiles  by  having  a  long  slender 
snout. 

Chameleons,  Lizards  and  Snakes. — The  order  Squamata 
is  divided  into  three  sub-orders:  the  Rhiptoglossi,  including  the 
chameleons,  the  Sauria,  including  the  lizards,  and  the  Serpentes, 
including  the  snakes.  The  true  chameleons  differ  from  the 
other  members  of  this  order  in  several  respects.  The  body  is 
laterally  compressed,  the  legs  are  long  and  slender,  and  the  toes 
are  grouped  so  that  two  of  them  are  opposed  to  the  other  three. 
The  tongue  can  be  projected  for  a  remarkable  distance  for 
capturing  insects.  Chameleons  are  of  interest  because  of  their 
power  of  rapidly  changing  their  colors.  The  color  is  usually 
greenish,  but  under  certain  stimuli,  such  as  light  and  tempera- 
ture, the  color  may  change  to  varied  shades  simulating  the 
surrounding  objects.  This  change  of  color  is,  seemingly  at 
least,  partially  under  control  of  the  animal.  None  of  the  mem- 
bers of  this  sub-order  occurs  in  America,  but  there  is  found  in 
the  southern  states  a  beautiful  green  lizard,  Anolis  principalis, 


266    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


that  has  the  power  of  changing  its  color  to  a  considerable 
degree  and  so  is  popularly  called  a  chameleon. 

The  group  of  lizards  is  a  very  large  one,  the  species  being 
especially  abundant  in  the  tropics.  The  skin  is  covered  with 
many  small  scales,  and  the  legs  are  fitted  for  running,  but  the 


FIG.  1 20. — A  fence  lizard,  Sceloporus  occidentalis. 

body  is  usually  dragged  along  the  ground  and  not  wholly 
lifted  by  the  legs.  The  jaws  are  furnished  with  teeth.  Lizards 
feed  principally  upon  insects,  and  some  of  the  species  may  be 
of  considerable  importance  in  controlling  noxious  forms. 
Although  the  lizards  are  often  regarded  as  being  poisonous 


FIG.  121. — The  Gila  monster,  Hcloderma  suspectum,  the  only  poisonous 
lizard.     (After  Snyder.) 

the  members  of  only  a  single  genus,  Heloderma,  are  really  so. 
This  genus  includes  the  Gila  monster  found  in  New  Mexico, 
Arizona  and  northern  Mexico.  It  is  a  heavy-bodied,  deep 
black,  orange-mottled  lizard,  twelve  to  sixteen  inches  long. 
The  poison  is  secreted  by  glands  in  the  lower  jaw  and  flows 


SNAKES,  LIZARDS,  TURTLES,  AND  CROCODILES  267 

along  the  grooved  teeth  into  the  wound.  The  bite  of  this  ill- 
looking  reptile  may  be  very  serious. 

The  most  common  lizards  in  this  country  are  the  swifts 
and  ground  lizards  that  are  so  numerous  in  many  gravelly 
and  bushy  places.  They  may  often  be  seen  sunning  themselves 
on  rocks,  fences  or  other  exposed  places.  They  are  all  very 
timid.  An  interesting  member  of  this  group  is  the  glass  snake, 
or  joint-snake.  Having  no  external  limbs  it  is  commonly 
considered  to  be  a  snake  rather  than  a  lizard.  Its  tail  is  so 
brittle  that  part  of  it  may  break  off  at  the  slightest  pull  or  blow. 
In  time  a  new  tail  is  regenerated.  Many  other  lizards 
possess  this  power  of  easily  breaking  off  a  portion  of  the  tail. 
It  will  be  seen  that  this  may  often  be  of  considerable  impor- 
tance to  the  lizard,  for  if  it  is  pursued  by  an  enemy  the  part 
most  likely  to  be  seized  is  the  tail,  and  if  this  can  be  broken  off 
the  lizard  may  escape  and  in  time  the  lost  part  be  replaced. 

In  the  desert  regions  of  the  Southwest  are  found  several 
species  of  the  peculiar  little  lizard  commonly  known  as  the 
horned  toad,  genus  Phrynosoma.  The  body  is  shortened, 
much  flattened,  and  furnished  with  a  number  of  spine-like 
scales.  These  spines  are  particularly  well-developed  in  a 
row  along  the  hind  margin  of  the  head.  The  color  of  these 
animals  resembles  very  closely  the  soil  or  rocks  where  they  are 
found.  This  protecting  coloration  doubtless  helps  to  save 
them  from  their  enemies.  In  the  tropics  many  of  the  lizards 
attain  a  great  size,  and  are  of  strange  shapes  and  patterns. 
Some  of  the  tree-inhabiting  forms  are  very  beautifully  colored. 
The  iguanas  in  South  America  often  reach  a  length  of  five  or 
six  feet,  and  are  much  used  for  food. 

The  appendages  are  entirely  absent  in  most  of  the  snakes. 
A  few  species,  however,  have  a  pair  of  spur-like  projections 
on  the  hinder  part  of  the  body,  doubtless  vestiges  of  the  hind 
legs.  The  lower  side  of  the  body  in  front  of  the  anus  is  covered 
with  broad  scales,  called  abdominal  scutes,  which  extend 
from  one  side  of  the  body  to  the  other.  The  ends  of  these 
broad  scales  are  attached  to  the  ribs,  and  the  free  posterior 
edges  may  be  drawn  forward  slightly  and  pressed  against  the 
surface  on  which  the  snake  is  lying  so  that  when  they  are 


268    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

drawn  back  again  the  body  of  the  snake  is  thrust  forward. 
It  is  the  movement  of  these  scutes,  accompanied  by  the 
undulations  of  the  body,  that  enables  the  snake  to  crawl  so 
rapidly.  They  cannot  move  forward  on  smooth  surfaces 
because  the  scutes  have  nothing  to  catch  against.  The  scales 
on  the  head  are  quite  regular  in  their  arrangement,  forming 
definite  patterns.  The  bones  of  the  jaws  are  so  arranged 
that  the  mouth  is  very  distensible.  This  allows  the  snakes 
to  swallow  objects  which  are  greater  in  size  than  the  normal 
diameter  of  the  body  and  it  is  not  an  unusual  sight  to  see  a 


FIG.  122. — A  garter-snake,  Thamnophis  parietalis.     (After  Snyder.) 

snake  with  a  part  of  its  body  very  greatly  distended  by 
some  small  animal  that  it  has  swallowed  whole.  The  tongue 
is  slender,  protrusible  and  deeply  notched.  It  is  commonly 
supposed  that  the  tongue  can  inflict  injury,  but  this  is  not 
true.  It  doubtless  serves  as  a  special  organ  of  touch.  The 
teeth  are  sharp  and  recurrent.  In  the  poisonous  snakes  cer- 
tain of  the  teeth  develop  into  long  sharp  fangs  which  are 
grooved  or  tubular  and  serve  to  conduct  the  poison  from  the 
poison  gland  in  the  head  into  the  wound.  The  food  of  snakes 
consists  very  largely  of  other  animals  which  are  usually  caught 
alive.  Many  species  feed  on  the  eggs  of  other  animals.  Many 
persons  erroneously  regard  all  snakes  as  dangerous,  and  try  to 
kill  all  that  they  see.  But  most  of  our  common  kinds  are  not 
only  harmless  but  very  serviceable  because  they  destroy  mice, 


SNAKES,  LIZARDS,  TURTLES,  AND  CROCODILES  269 

ground  squirrels  or  other  pests.  The  blind  snakes,  genus 
Glaucoma,  burrow  in  the  earth  and  feed  on  insect  larva  and 
worms. 

Among  the  most  familiar  of  the  many  non-poisonous  snakes 
are  the  striped  garter-snakes,  genus  Thamnophis,  found  every- 
where in  the  fields  and  gardens.  The  common  water-snake, 
genus  Natrix,  is  only  semi-aquatic,  spending  most  of  the  time 
on  land  in  the  vicinity  of  ponds  or  streams.  They  are  ex- 
cellent swimmers  and  quickly  take  to  the  water  when  alarmed. 
The  large  blacksnake,  Zamenis  constrictor,  and  the  blue-racer, 


FIG.  123. — A  king-snake,  Lampropeltis  boyli.     (After  Snyder.) 

which  is  merely  a  color  variety  of  the  same  species,  are  common 
in  open  meadows,  where  they  feed  on  frogs,  mice,  eggs,  young 
birds  and  other  animals  which  they  swallow  alive.  The 
king-snakes,  genus  Ophibolus,  are  so  called  because  they  feed 
on  other  snakes.  They  seem  to  be  immune  to  the  venom  of  the 
poisonous  snakes  and  readily  attack  any  of  them.  The  puff- 
adders,  or  spreading  vipers,  or  blow-snakes,  genus  Heterodon, 
are  commonly  supposed  to  be  poisonous  but  are  really  quite 
harmless.  No  American  snake  with  slender,  sub-parallel- 
sided  head  is  poisonous. 

The  dreaded  rattlesnakes,  and  the  copperheads  and  water- 
moccasins,  are  thick-bodied  venomous  snakes  with  flat,  tri- 
angular heads  and  with  strong  tubular  fangs  which  are  folded 
flat  against  the  roof  of  the  mouth  when  it  is  closed.  When 


27o    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  snake  strikes,  these  fangs  are  lowered  and  thrust  into 
the  victim  and  the  poison,  which  is  secreted  by  small  glands  in 
the  head,  is  injected  through  them.  There  are  several  species 
of  rattlesnakes,  all  belonging  to  the  genus  Crotalus.  They  are 
most  abundant  in  the  Southwest,  but  are  found  in  almost  all 
parts  of  the  United  States  except  in  the  higher  mountains. 
The  rattle  on  the  tail  is  composed  of  a  series  of  partly  overlap- 
ping thin  horny  pieces,  the  somewhat  modified  successively 
formed  epidermal  coverings  of  the  tip  of  the  body.  A  new  rattle 
is  added  each  time  the  snake  sheds  its  skin,  and  as  the  snakes 
usually  molt  about  three  times  a  year  the  age  of  a  rattlesnake 
may  be  approximately  estimated  provided  none  of  the  terminal 
units  of  the  rattle  has  been  lost. 


FIG.  124. — The  rattles  of  the  rattlesnake.     The  lower  figure  shows  a  longi- 
tudinal section  of  the  rattle. 

The  chestnut-colored  copperheads,  Agkistrodon  contortrix, 
occur  throughout  the  eastern  and  middle  United  States.  They 
are  very  vicious  and  dangerous,  striking  without  warning. 
The  water-moccasin,  Agkistrodon  pisciwris,  of  the  southern 
states  is  the  most  dangerous  of  our  serpents.  It  is  found  in 
swampy  places  and  in  the  water.  It  is  ill-tempered  and  aggres- 
sive, striking  on  the  slightest  provocation.  The  poisonous 
harlequins  or  coral-snakes,  Elapsfulvius,  that  live  in  the  south- 
eastern United  States,  are  also  very  venomous.  They  are 
black,  very  strikingly  marked  by  broad,  yellow-bordered, 
crimson  rings. 


SNAKES,  LIZARDS,  TURTLES,  AND  CROCODILES  271 


Notwithstanding  the  fact  that  a  bite  from  any  one  of  these 
venomous  snakes  may  prove  fatal  to  man  in  a  very  short  time, 
the  real  danger  from  these  snakes  is  not  as  great  as  it  would 
seem,  for  they  may  usually  be  seen  or  heard  and  avoided.  The 
number  of  deaths  resulting  from  snake  bites  in  the  United 
States  each  year  is  very  small  indeed,  an  average  of  but  only 
two  each  year,  it  has  been  estimated.  Sucking  the  blood  and 
poison  from  the  wound  or  drinking  large  quantities  of  whiskey 
are  the  two  methods  most  commonly  recommended  for  treat- 
ing snake  bites.  Sucking  the  poison  from  the  wound  may  do 
some  good  but  it  is  very  dangerous,  for  should  some  of  the  poi- 
son get  into  cuts  or  abrasions 
on  the  lips  or  in  the  mouth 
it  might  cause  more  harm 
that  it  would  in  the  original 
wound.  Excessive  use  of  al- 
coholic drinks  must  also  be 
avoided,  as  experiments  have 
shown  that  they  may  exert 
a  very  unfavorable  effect. 
The  best  thing  to  do  if  one 
should  be  bitten  by  a  poi- 
sonous snake  is  to  apply  pres- 
sure, by  a  ligature  or  other- 
wise, to  the  blood-vessels  lead- 
ing from  the  wound  to  the 

heart  to  prevent  the  blood  from  carrying  the  poison  to  the 
heart.  If  a  physician  is  not  available  within  a  very  short 
time  the  tissue  around  the  wound  should  be  incised  deeply  and 
a  solution  of  potassium  permanganate  (i  part  of  the  chemical 
to  zoo  parts  of  water)  injected.  If  properly  and  promptly 
applied  such  a  treatment  may  destroy  much  of  the  venom 
before  it  can  reach  the  heart  and  be  sent  from  there  over  the 
whole  system.  Hypochlorite  of  calcium,  i  part  to  60  parts  of 
water,  or  chloride  of  gold,  i  to  100,  or  chromic  acid,  i  to  100, 
may  be  used  if  the  potassium  permanganate  is  not  available. 
When  the  venom  of  a  poisonous  snake  is  introduced  into  the 
blood  of  an  animal  in  small  quantities  it  is  capable  of  pro- 


FIG.  125. — Dissection  of  head  of 
rattlesnake.  /,  poison-fangs;  p, 
poison-sac. 


272    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

ducing  a  substance  called  antivenin  which  neutralizes  the 
effect  of  that  particular  kind  of  poison.  In  regions  where 
snake  bites  are  of  frequent  occurrence  the  antivenin  for  the 
most  dangerous  snakes  is  prepared  and  kept  ready  for  use.  A 
small  amount  of  it  injected  into  the  blood-vessels  soon  after  a 
snake  has  bitten  a  person  usually  counteracts  the  effects  of 
the  venom.  Most  dangerous  of  all  the  poisonous  snakes  is  the 
dreaded  cobra  of  India,  Naja  tripudians,  a  very  vicious  and 
most  deadly  reptile.  Twenty-five  to  55  per  cent,  of  cobra  bites 
prove  fatal,  and  the  annual  loss  of  human  lives  in  India  from 
this  snake  is  often  over  20,000.  The  sea-snakes,  which  inhabit 
many  tropical  seas,  attaining  a  length  of  six  or  eight  feet,  are 
also  very  poisonous.  The  body  is  often  compressed  thus  better 
fitting  them  for  their  aquatic  life.  They  do  not  leave  the  water 
even  to  breed,  but  give  birth  to  their  living  young  while  at  sea. 
The  pythons,  genus  Python,  which  sometimes  attain  a 
length  of  twenty  or  thirty  feet,  and  the  smaller  boas  or  boa- 
constrictors,  Boa  constrictor,  are  not  venomous.  They  kill 
their  prey  by  coiling  their  body  around  it  and  crushing  it. 
These  are  tropical  or  semi-tropical  snakes. 


CHAPTER  XXIV 
BIRDS 

The  birds,  class  Aves,  the  most  familiar  and  attractive  of 
wild  animals,  have  been  the  object  of  so  much  attention  and 
study  by  professional  naturalists,  amateur  nature  students  and 
just  nature  lovers,  that  their  classification,  life  history  and 
habits  are  better  known  than  are  those  of  any  other  animal 
group. 

About  i2,oool  different  species  of  birds  are  known  from  all 
the  world,  of  which  about  800  occur  in  North  America.  In 
any  single  favorable  locality  in  this  country  one  can  get  ac- 
quainted with  from  100  to  200  species,  counting  in  those 
kinds  that  pass  in  the  fall  and  spring  migrations  as  well 
as  those  that  nest  in  the  locality.  The  number  of  kinds 
that  may  be  called  ''all-year  residents,"  that  is,  which 
remain  in  the  same  region  through  the  whole  year,  is,  however, 
very  small,  averaging  usually  about  one-seventh  of  the  total 
number  that  may  be  seen  in  the  region  during  the  course  of  a 
year.  This  limited  number  of  kinds  of  birds  in  any  one 
locality,  together  with  the  bright  colors  and  characteristic 
manners  which  make  their  identification  easy,  the  interest 
of  their  songs  and  flight  and  their  feeding,  nesting  and  general 
domestic  habits,  make  birds  excellent  subjects  for  personal 
field  studies  by  students.  And  if  the  food  habits  are  studied 
from  an  economic  point  of  view,  valuable  practical  informa- 
tion can  be  obtained  during  the  study. 

General  Structure. — The  general  body  form  and  external 
appearance  of  a  bird  are  too  familiar  to  need  description. 
The  covering  of  feathers,  the  modification  of  the  fore  limbs 

1  The  British  Museum   Catalogue  lists  nearly   19,000  species    but  it 
recognizes  as  full  species  about  7000  forms  considered  by  most  ornitholo- 
gists to  be  merely  varieties  or  sub-species. 
18  273 


274    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

into  wings,  and  the  toothless,  beaked  mouth  are  characteristic 
and  distinguishing  external  features.  The  feathers,  although 
covering  the  whole  of  the  surface  of  the  body,  are  not  uni- 
formly distributed,  but  are  grouped  in  tracts  called  pterylce, 
separated  by  bare  or  downy  spaces  called  apteria.  They  are 
of  several  kinds,  the  short  soft  plumules,  or  down  feathers,  the 
large,  stiffer,  contour  feathers,  whose  ends  form  the  outermost 


FIG.  126. — A   body   feather  and   a   wing   feather   from   a   chicken. 
(Reduced.) 

covering  of  the  body,  the  quill  feathers  of  the  wings  and  tail, 
and  the  fine  bristles,  or  vibrissae,  about  the  eyes  and  nostrils, 
called  thread  feathers.  The  fore  limbs  are  modified  to  serve 
as  wings,  which  are  well  developed  in  almost  all  birds.  How- 
ever, the  strange  kiwi,  or  Apteryx,  of  New  Zealand  with  hair- 
like  feathers  is  almost  wingless,  and  the  penguins  have  the 
wings  so  reduced  as  to  be  incapable  of  flight,  but  serving 
as  flippers  to  aid  in  swimming  underneath  the  water.  The 


BIRDS 


275 


a 


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P 


o 

£ 


276    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

ostriches  and  cassowaries  also  have  only  rudimentary  wings 
and  are  not  able  to  fly.  Legs  are  present  and  functional  in 
all  birds,  varying  in  relative  length,  shape  of  feet,  etc.,  to  suit 
the  special  perching,  running,  wading,  or  swimming  habits  of 
the  various  kinds.  Living  birds  are  toothless,  although  certain 
extinct  forms,  known  through  fossils,  had  on  both  jaws 
large  teeth  set  in  sockets.  The  place  of  teeth  is  taken,  as  far  as 
may  be,  by  the  bill  or  beak  formed  of  the  two  jaws,  projecting 
forward  and  tapering  more  or  less  abruptly  to  a  point.  In 
most  birds  the  jaws  or  mandibles  are  covered  by  a  horny 
sheath.  In  some  water  and  shore  forms  the  mandibular 
covering  is  soft  and  leathery.  The  range  in  size  of  birds  is 
indicated  by  comparing  a  humming-bird  with  an  ostrich. 

Many  of  the  bones  of  birds  are  hollow  and  contain  air.  The 
air-spaces  in  them  connect  with  air-sacs  in  the  body,  which 
connect,  in  turn,  with  the  lungs.  Thus  a  bird's  body  contains 
a  large  amount  of  air.  The  breastbone  is  usually  provided 
with  a  marked  ridge  or  keel  for  the  attachment  of  the  large 
and  powerful  muscles  that  move  the  wings,  but  in  those 
birds  like  the  ostriches,  which  do  not  fly  and  have  only  rudi- 
mentary wings,  this  keel  is  greatly  reduced  or  wholly  wanting. 
The  fore  limbs  or  wings  are  terminated  by  three  "fingers" 
only.  The  legs  have  usually  four  toes,  although  a  few  birds 
have  only  three  toes  and  the  ostriches  but  two. 

As  birds  have  no  teeth  with  which  to  masticate  their  food, 
a  special  region  of  the  alimentary  canal,  the  gizzard,  is  provided 
with  strong  muscles  and  a  hard  and  rough  inner  surface  by 
means  of  which  the  food  is  crushed.  Seed-eating  birds  have . 
the  gizzard  especially  well  developed,  and  some  birds  take  small 
stones  into  the  gizzard  to  assist  in  the  grinding.  The  lungs 
of  birds  are  more  complex  than  those  of  amphibians  and  rep- 
tiles, being  divided  into  small  spaces  by  numerous  membranous 
partitions.  They  are  not  lobed,  as  in  mammals,  and  do  not 
lie  free  in  the  body  cavity,  but  are  fixed  to  the  inner  dorsal 
region  of  the  body.  Connected  with  the  lungs  are  the  air- 
sacs  already  referred  to,  which  are  in  turn  connected  with  the 
air-spaces  in  the  hollow  bones.  By  this  arrangement  the  bird 
can  fill  with  air  not  only  its  lungs  but  all  the  special  air-sacs 


BIRDS  277 

and  spaces.  The  special  function  of  these  air-sacs  in  not  un- 
derstood; many  believe  that  in  some  way  they  aid  the  bird  in 
its  flight  or  in  respiration.  The  vocal  utterances  of  birds  are 
produced  by  the  vocal  cords  of  the  syrinx  or  lower  larynx, 
situated  at  the  lower  end  of  the  trachea  just  where  it  divides 
into  the  two  bronchial  tubes,  the  tracheal  rings  being  here 
modified  so  as  to  produce  a  voice-box  containing  two  vocal 
cords  controlled  by  five  or  six  pairs  of  muscles.  The  air  passing 
through  the  voice-box  strikes  against  the  vocal  cords,  the  ten- 
sion of  which  can  be  varied  by  the  muscles.  In  mammals 
the  voice-organ  is  at  the  upper  or  throat  end  of  the  trachea. 

The  heart  of  birds  is  composed  of  four  distinct  chambers, 
the  septum  between  the  two  ventricles,  incomplete  in  the 
Reptilia,  being  complete  in  this  group.  There  is  thus  no 
mixing  of  arterial  and  venous  blood  in  the  heart.  The  sys- 
temic blood  circulation  being  completely  separated  from  the 
pulmonic,  the  circulation  is  said  to  be  double.  The  circula- 
tion of  birds  is  active  and  intense;  they  have  the  hottest 
blood  and  the  quickest  pulse  of  all  animals.  In  them  the 
brain  is  compact  and  large,  and  more  highly  developed  than 
in  amphibians  and  reptiles,  but  the  cerebrum  has  no  convolu- 
tions as  in  the  mammals.  Of  the  special  senses  the  organs 
of  touch  and  taste  are  apparently  not  keen;  those  of  smell, 
hearing,  and  sight  are  well  developed.  The  optic  lobes  of  the 
brain  are  of  great  size,  relatively,  compared  with  those  of  other 
vertebrate  brains,  and  there  is  no  doubt  that  the  sight  of  birds 
is  keen  and  effective.  The  power  of  accommodation,  or  of 
quickly  changing  the  focus  of  the  eye,  is  highly  perfected. 
The  structure  of  the  ear  is  comparatively  simple,  there  being 
ordinarily  no  external  ear,  other  than  a  simple  opening.  The 
organs  of  the  inner  ear,  however,  are  well  developed,  and 
birds  undoubtedly  have  excellent  hearing.  The  nostrils  open 
upon  the  beak,  and  the  nasal  chambers  are  not  at  all  complex, 
the  smelling  surface  being  not  very  extensive.  It  is  probable 
that  the  sense  of  smell  is  not,  as  a  rule,  especially  keen. 

Development  and  Life  History. — All  birds  are  hatched  from 
eggs,  which  undergo  a  longer  or  shorter  period  of  incubation 
outside  the  body  of  the  mother,  and  which  are,  in  most  cases. 


278    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

laid  in  a  nest  and  incubated  by  the  parents.  The  eggs  are 
fertilized  within  the  body  of  the  female,  the  mating  time  of 
most  birds  being  in  the  spring  or  early  summer.  Some  kinds, 
the  English  sparrow,  for  example,  rear  numerous  broods  each 
year,  but  most  species  have  only  one  or  at  most  two.  The 
eggs  vary  greatly  in  size  and  color-markings,  and  in  number 
from  one,  as  with  many  of  the  Arctic  ocean  birds,  to  six  or 
ten,  as  with  most  of  the  familiar  song-birds,  or  from  ten  to 
twenty,  as  with  some  of  the  pheasants  and  grouse.  The  dura- 
tion of  incubation  (outside  the  body)  varies  from  ten  to  thirty 
days  among  the  more  familiar  birds,  to  nearly  fifty  among  the 
ostriches.  The  temperature  necessary  for  incubation  is  about 
40°  C.  (100°  F.).  Among  polygamous  birds  (species  in  which 
a  male  mates  with  several  or  many  females)  the  males  take  no 
part  in  the  incubation  and  little  or  none  in  the  care  of  the 
hatched  young;  among  most  monogamous  birds,  however,  the 
male  helps  to  build  the  nest,  takes  his  turn  at  sitting  on  the 
eggs,  and  is  active  in  bringing  food  for  the  young,  and  in  de- 
fending them  from  enemies.  The  young,  when  ready  to  hatch, 
break  the  egg-shell  with  the  "egg-tooth,"  a  horny,  pointed 
projection  on  the  upper  mandible,  and  emerge  either  blind 
and  almost  naked,  dependent  upon  the  parents  for  food  until 
able  to  fly  (altricial  young),  or  with  eyes  open  and  with  body 
covered  with  down,  and  able  in  a  few  hours  to  feed  themselves 
(precocial  young). 

Classification. — The  class  Aves  is  usually  divided  into 
numerous  orders,  the  number  and  limits  of  these  as  published 
in  zoological  manuals  varying  according  to  the  opinions  of 
various  zoologists.  The  rank  of  an  order  in  this  group  is  far 
lower  than  in  most  other  classes.  In  other  words,  the  orders 
are  very  much  alike  and  are  recognized  mainly  for  the  con- 
venience in  breaking  up  the  vast  assemblage  of  species.  In 
North  America  most  of  the  ornithologists  have  agreed  upon  a 
scheme  of  classification,  which  will  therefore  be  adopted  in 
this  book.  This  classification,  together  with  a  complete 
catalogue  of  all  North  American  bird  kinds,  is  published  by 
the  American  Ornithologists  Union  as  a  "Checklist  of  North 
American  Birds."  According  to  this  classification  the  800 


BIRDS 


279 


(approximately)  known  species  of  North  American  birds 
represent  seventeen  orders.  Certain  recognized  orders,  for 
example,  the  ostriches,  are  not  represented  naturally  in 
North  America  at  all. 

Ostriches. — The  old  order  Ratitas  (now  divided  into  several 
smaller  orders)   or  birds  without  keeled  breastbone,  as  the 


FIG.  128. — Ostriches  on  ostrich  farm  at  Pasadena,  California. 

ostriches,  cassowaries,  rheas,  etc.,  is  not  represented  naturally 
in  this  country,  but  in  California,  Arizona,  Florida,  and  a 
few  other  states,  the  African  ostrich,  Struthio  camelus,  is  being 
bred  and  reared  on  "ostrich  farms"  for  the  sake  of  its  plumes. 
This  is  the  largest  living  kind  of  bird,  specimens  attaining 
the  height  of  eight  feet  and  the  weight  of  300  pounds.  The 


280    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

eggs,  which  are  five  to  six  inches  long  and  nearly  as  thick, 
are  laid  naturally  in  shallow  hollows  scooped  out  in  the  sand 
of  the  desert,  and  the  hot  sun  and  the  male  birds  do  most  of 
the  incubating.  The  young  hatch  in  from  seven  to  eight 
weeks,  and  can  run  about  immediately. 

Ostriches  used  to  be  hunted  and  killed  for  their  feathers,  but 
since  the  discovery  that  they  can  be  reared  in  confinement  and 
a  superior  quality  of  plumes  thus  obtained,  their  hunting  has 
been  given  up.  They  have  been  domesticated  in  South 
Africa  since  about  1865,  and  now  about  half  a  million  tame 
birds  exist  there.  The  present  annual  value  of  the  ostrich 
plume  output  is  about  $10,000,000.  Good  average  birds  will 
produce  $50  worth  of  feathers  a  year,  and  are  worth  from 
$700  to  $1000  a  pair.  The  plumes  grow  on  the  rudimentary 
wings  and  tail,  and  the  plucking  does  not  hurt  the  birds  in  any 
way. 

Water  and  Shore  Birds. — The  typical  water  birds  include  the 
order  Pygopodes,  or  loons,  grebes,  auks,  etc. ;  the  Longipennes, 
or  gulls,  terns,  petrels  and  albatrosses;  the  Steganopodes,  or 
cormorants,  pelicans,  and  boobies;  and  the  Anseres,  or  swans, 
geese  and  ducks.  Among  these  the  cormorants  and  gulls 
are  of  some  special  use  to  man  as  scavengers  along  the  sea- 
shore, the  gulls  especially  doing  much  to  rid  harbors  of  refuse 
thrown  overboard  by  the  ships.  But  it  is  among  the  Anseres 
especially  that  are  found  the  water  birds  that  interest  the 
economic  zoologist  particularly.  The  order  includes  about 
sixty  North  American  species,  of  which  three  are  swans, 
sixteen  geese,  and  the  rest  ducks.  In  all,  the  bill  is  more  or 
less  flattened  and  is  also  lamellate,  i.e.,  furnished  along  each 
cutting  edge  with  a  regular  series  of  tooth-like  ridges.  The 
feet  are  webbed  and  the  legs  short  and  set  far  back  on  the  body, 
an  adaptation  for  effective  swimming.  The  food  consists  of 
roots  and  seeds  of  plants,  worms,  insects,  small  molluscs  and 
even  small  fishes,  and  only  in  occasional  instances,  as  in  the 
invasion  of  grain  fields  by  geese,  are  the  food  habits  likely  to 
cause  loss  to  man. 

On  the  other  hand,  both  geese  and  ducks  are  among  our  most 
abundant  and  largest  game  birds,  and  certain  species,  such  as 


BIRDS  281 

the  Canada  goose  and  the  mallard,  teal,  pintail,  widgeon, 
shoveller  or  spoonbill,  canvasback,  redhead,  bluebill  and  other 
ducks,  provide  not  only  sport,  but  very  enjoyable  food  during 
the  shooting  season.  Of  these  perhaps  the  most  notable  are 
the  mallard,  which  is  primarily  a  fresh  water  duck  and  is  the 
ancestor  of  most  of  our  domesticated  races,  and  the  canvasback, 
a  salt  water  species  especially  abundant  from  Chesapeake  Bay 
south  along  the  Carolina  Coast,  and  on  the  whole,  more  prized 
for  its  flavor  than  any  other  duck.  The  special  flavor  of  the 
east  coast  canvasback  may  be  due  to  its  feeding  largely  on 
wild  celery  ( Vail isneria) .  To  the  uneducated  palate,  however, 
the  milder-flavored  fresh  water  or  river  ducks  will  be  more 
enjoyable  than  the  canvasbacks,  redheads  and  bluebills  of 
the  coast  waters. 

The  wading  and  shore  birds  include  the  order  Herodiones, 
or  ibises,  herons  and  bitterns,  the  Paludicola,  cranes,  rails  and 
coots,  and  the  LimicolfS,  comprising  the  plover,  curlew, 
sandpipers  and  snipes.  These  orders  include  numerous  game 
birds  such  as  the  rails,  woodcock,  jacksnipe,  various  plovers, 
curlews,  yellowlegs  and  sandpipers.  In  rare  instances  cranes 
may  invade  grain  fields,  but  the  food  of  most  of  the  waders 
is  obtained  from  the  marshes  or  bay  and  lake  shores,  and 
consists  chiefly  of  small  animals,  running  all  the  way  from  frogs 
down  to  insects.  The  rails,  however,  have  a  fondness  for 
seeds,  especially  wild  rice,  and  the  clapper  rail  and  sora,  or 
Carolina  rail,  become  very  fat  in  the  autumn  and  are  much 
hunted  in  the  marshes  of  the  South  Atlantic  States.  The 
woodcock  frequents  thick  brush  and  covert  in  the  Eastern  States 
and  lies  there  concealed  in  daytime,  issuing  at  dusk  to  search 
for  food  on  marshy  ground.  It  is  thus  rather  owl-like  in  habit 
and  with  its  big  head  and  eyes  is  indeed  rather  owl-like  in 
appearance  except  of  course  for  its  long  bill  and  snipe's  legs. 
Its  flesh  is  highly  esteemed,  but  in  the  absence  of  suitably 
protecting  game  laws  it  has  been  so  ruthlessly  shot  for  market 
that  it  is  already  a  vanishing  species.  The  jacksnipe,  or  Wil- 
son's snipe,  common  over  the  whole  country,  is  one  of  the  best 
known  of  game  birds.  It  is  a  swift,  erratic  flyer,  and  fre- 
quents open  marshy  ground.  The  golden  plover  is  a  special 


282    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

favorite  for  its  flesh  but  it  has  been  so  persistently  shot  that 
its  numbers  have  been  greatly  lessened. 

The  Pheasants  and  Doves  (Orders  Gallina  and  Columbce). — 
The  Gallina  include  most  of  the  domestic  fowls,  as  the  hen, 
turkey,  peacock  and  guinea  fowls.  They  include  also  the  chief 
game  birds  of  most  countries,  as  the  grouse,  quail,  partridges, 
wild  turkey,  ptarmigan,  etc.  They  all  have  the  bill  rather 


FIG.  129. — The  common  Eastern  quail,  or  Bob-white,  Colinus  virginianus. 
(Photograph  by  J.  M.  Slonaker.) 

short,  heavy,  convex  and  bony,  adapted  for  picking  up  and 
crushing  seeds  and  grains  which  compose  their  principal  food. 
They  are  mostly  terrestrial  in  habit  and  are  sometimes  known 
as  the  Rasores,  or  "scratchers."  The  eggs  are  numerous,  and 
are  laid  in  a  rude  nest  or  simply  in  a  depression  on  the  ground. 
In  many  of  the  species  polygamy  is  the  rule.  The  young  are 
precocial.  Among  the  more  familiar  wild  gallinaceous  birds 


BIRDS  283 

are  the  eastern  quail,  or  "bob-white,"  abundant  in  the  eastern 
and  central  United  States,  the  ruffed  grouse  of  the  eastern 
woods,  and  the  prairie  chicken  of  the  western  prairies.  Besides 
the  bob-white  there  are  five  other  quail  species  in  this  country, 
all  of  which  live  in  western  and  especially  southwestern 
regions.  The  examination  of  many  stomachs  has  shown  that 
more  than  50  per  cent,  of  the  food  of  all  these  quail  is  weed 
seeds.  The  rest  is  composed  of  insects,  some  grains,  and  a 
miscellany  comprising  leaves,  buds,  spiders,  myriapods,  crusta- 
ceans, etc.  The  bob- white  eats  about  83  \  per  cent,  vegetable 
matter  and  i6|  per  cent,  animal  matter.  As  the  weed  seeds 
and  insects  together  compose  the  major  part  of  the  food,  quails 
are  far  more  beneficial  than  hurtful  to  the  farmer. 

The  doves  and  pigeons  constitute  the  small  order  Columba, 
closely  related  to  the  Gallince.  The  bill  is  covered  at  the  base 
by  a  soft  swollen  membrane,  or  cere,  in  which  the  nostrils  open. 
The  food  consists  of  fruits,  seeds  and  grains.  The  most 
familiar  wild  species  is  the  mourning  dove,  or  turtle  dove,  which 
occurs  all  over  the  country,  and  is  shot  as  a  game  bird  in  some 
states.  The  beautiful  passenger  pigeon,  formerly  extremely 
abundant,  moving  about  in  enormous  flocks  in  the  eastern  and 
central  states,  has  been  exterminated  by  ruthless  killing.  All 
the  various  kinds  of  domestic  pigeons  such  as  pouters,  fantails 
carriers,  ruff-necks,  tumblers,  etc.,  are  believed  to  be  the  modi- 
fied descendants  of  the  common  European  rock  dove,  Columba 
lima. 

Other  Land  Birds. — Of  the  other  land  birds,  besides  the 
Gallina  and  Columba,  about  one-half  belong  to  the  order 
Passeres.  or  perching  birds.  The  others  are  distributed  among 
the  orders  Raptores,  or  birds  of  prey,  Pici,  or  woodpeckers 
Coccyges,  or  cuckoos  and  kingfishers,  Macrochires,  or  whip- 
poorwills,  chimney-swifts  and  humming-birds,  and  the 
Psittaci,  or  parrots,  of  which  but  one  species,  the  small  Caro- 
lina parroquet,  exists  wild,  in  small  numbers,  in  the  United 
States.  It  is  found  only  in  Florida. 

The  Raptores  include  the  eagles,  hawks,  vultures  and  owls, 
and  their  food  habits  make  them  on  the  whole  decidedly  bene- 
ficial birds.  Of  the  fifty  or  more  species  of  eagles  and  hawks 


284    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

found  in  this  country  only  a  few  kinds  ever  raid  barnyards  or 
pastures,  while  the  same  kinds,  together  with  all  the  others, 
make  way  with  many  noxious  rodents  and  large  insects,  such 
as  grasshoppers,  crickets  and  June  bugs.  Their  captures  of 
other  birds  are,  however,  mostly  to  be  deplored,  and  two  species 
of  small  hawks,  Cooper's  hawk  and  the  sharp-shinned  hawk, 


FIG.  130. — Red-headed  woodpecker,  Melanerpes  erythroccphalus,  young  at 
opening  of  nest  to  receive  food  from  the  mother.  (Photograph  by  J.  M. 
Slonaker.) 


deserve  to  be  shot  on  sight,  for  they  feed  almost  entirely  on 
wild  birds  and  poultry. 

There  are  twenty-three  species  of  woodpeckers  in  the 
United  States,  and  the  food  of  twenty  of  them  consists  chiefly 
of  insects,  usually  wood-boring  grubs.  These  birds  do  much 
good  by  destroying  many  insect  pests  of  trees.  But  there 
are  three  kinds,  with  short  brushy  tongues  not  adapted  to 


BIRDS  285 

the  capture  of  insects,  which  do  some  injury  to  trees  by  feed- 
ing on  the  live  bark  and  sap  of  trees.  More  than  two  hundred 
and  fifty  kinds  of  trees,  shrubs  and  vines  are  attacked  by  these 
sap-suckers.  They  are  especially  fond  of  and,  hence,  hurtful 
to  hickory  trees.  The  common  sap-sucker  of  the  western 
states  is  the  only  woodpecker  in  that  region  that  has  the  whole 
head  and  throat  red,  while  the  common  one  of  the  middle  and 
eastern  states  is  the  only  one  having  the  front  of  the  head  from 
bill  to  crown  red  and  a  black  patch  on  the  breast.  By  these 
marks  these  two  injurious  woodpeckers  can  be  distinguished 
from  the  others,  all  of  which  are  beneficial. 

The  Passeres  include  the  familiar  song  birds  and  the  great 
majority  of  the  birds  of  the  garden,  the  forest,  the  roadside 
and  the  field.  The  feet  of  these  birds  always  have  four  toes 
and  are  fitted  for  perching.  The  syrinx,  or  musical  apparatus, 
is  well  developed  in  most  of  them.  Nesting  and  domestic 
habits  are  various,  but  the  young  are  always  hatched  in  a 
helpless  condition,  and  have  to  be  fed  and  otherwise  cared  for 
by  the  parents  for  a  longer  or  shorter  time.  The  North  Ameri- 
can species  of  this  order  are  grouped  into  eighteen  families, 
as  the  fly-catcher  family  (Tyrannidce) ,  crow  family  (Corvidce), 
the  sparrows  and  finches  (Fringillidce) ,  the  swallows  (Hirun- 
dinidce),  the  thrushes,  robins  and  blue  birds  (Turdidce),  etc. 
In  this  small  book  nothing  can  be  said  of  the  various  species 
which  belong  to  this  order.  However,  as  the  Passerine  birds 
are  those  which  immediately  surround  us  and  which,  by 
their  familiar  songs  and  nesting  habits,  most  interest  us,  the 
outdoor  study  of  birds  by  beginning  students  will  usually 
be  devoted  chiefly  to  the  members  of  this  order,  and  many 
different  kinds  will  soon  become  familiar.  The  robin  and 
blue  bird  will  introduce  us  to  their  shy  and  familiar  relatives, 
the  song  thrushes;  the  study  of  the  king  bird  or  bee-martin 
will  interest  us  in  some  of  the  other  fly-catchers.  From  the 
familiar  chipping  sparrow  and  tree-sparrow  we  shall  be  led  to 
look  for  their  cousins  the  swamp- sparrows  and  the  larger 
grosbeaks  and  crossbills,  and  so  on  through  the  order. 

Determining  and  Studying  the  Birds  of  a  Locality. — To 
identify  the  various  species  of  birds  in  the  locality  of  a  school 


286    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

it  will  be  necessary  to  have  some  book  giving  the  descriptions 
of  all  or  most  of  the  species  of  the  region,  with  tables  and  keys 
for  tracing  out  the  different  forms.  Such  bird  manuals  and 
keys  are  numerous  now,  as,  because  of  the  popular  interest 
in  bird  study,  many  bird  books  have  been  published  in  the 
last  few  years.  The  best  general  manual  is  Coues'  "Key 
to  the  Birds  of  North  America"  (sth  ed.,  2  vols.).  Chapman's 
"Handbook  of  the  Birds  of  Eastern  North  America,"  and 
Florence  Bailey's  "Handbook  of  Birds  of  Western  United 
States,"  are  each  complete  for  the  regions  covered  by  them. 
There  are  other  books  that  attempt  to  make  it  possible  by  keys 
based  chiefly  on  color  and  pattern  differences  to  distinguish 
the  birds  without  having  their  dead  bodies  actually  in  hand, 
which  usually  means  shooting  the  bird.  There  are  several 
magazines  devoted  to  accounts  of  the  life  and  habits  of  birds. 
Of  these  "Birdlore"  is  the  organ  of  the  Audubon  Society  for 
the  Protection  of  Birds,  and  is  an  accurate  but  popular  and 
beautifully  illustrated  journal.  Fig.  127  will  aid  the  stu- 
dent in  the  use  of  any  of  these  bird  books  by  making  him 
acquainted  with  the  names  of  the  various  external  parts  and 
special  plumage  regions  of  the  bird's  body. 

Birds  and  Seasons. — In  trying  to  become  acquainted  with 
the  birds  of  a  locality  it  must  be  borne  in  mind  that  the  bird- 
fauna  of  any  region  varies  with  the  season.  Some  birds  live 
in  it  all  the  year  through;  these  are  called  residents.  Some 
spend  only  the  summer  or  breeding  season  in  the  locality,  com- 
ing up  from  the  South  in  spring  and  flying  back  in  autumn; 
these  are  summer  residents.  Some  spend  only  the  winter  in 
the  locality,  coming  down  from  the  severer  North  at  the  be- 
ginning of  winter,  and  going  back  with  the  coming  of  spring; 
these  are  winter  residents.  Some  are  to  be  found  in  the 
locality  only  in  spring  and  autumn,  as  they  are  migrating  north 
and  south  between  their  tropical  winter  quarters  and  their 
northern  summer  or  breeding  home;  these  are  migrants.  And, 
finally,  an  occasional  representative  of  certain  bird  species, 
whose  normal  range  does  not  include  the  given  locality  at  all, 
will  appear  now  and  then,  blown  aside  from  its  regular  path 
of  migration,  or  otherwise  astray;  these  are  visitants.  As  to 


BIRDS  287 

the  relative  importance,  numerically,  of  these  various  cate- 
gories among  the  birds  which  may  be  found  in  a  certain  region, 
and  thus  form  its  bird-fauna,  we  may  illustrate  by  reference 
to  a  definite  region.  Of  the  351  species  of  birds  which  have 
been  found  in  the  state  of  Kansas  (a  region  without  distinct 
natural  boundaries,  and  fairly  representative  of  any  Mississippi 
valley  region  of  similar  extent),  51  are  all-year  residents,  125 
are  summer  residents,  36  are  winter  residents,  104  are  migrants, 
and  35  are  rare  visitants. 


FIG.  131. — Nest  of  song  sparrow  (Melospiza  cinerea). 
(Photograph  by  J.  H.  Paine) 

The  all-year  residents  and  the  summer  residents,  comprising 
about  one-half  of  the  species  to  be  found  in  a  locality,  are  the 
only  ones  which  breed  there,  and  which  thus  present  oppor- 
tunity for  observations  on  their  nest-building  habits  and  care 
of  the  young.  Numerous  suggestive  questions  present  them- 
selves in  connection  with  breeding.  Why  is  it  that  some 
species  nest  early  and  some  late?  Can  the  character  of  the 
food  of  the  young  have  anything  to  do  with  this?  If  so,  what? 
Does  the  condition  of  the  particular  trees,  bushes  or  other 
favorite  sites  for  nests  help  determine  the  nesting  time?  Why 


288    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

should  some  birds  raise  but  one  brood  a  year,  and  others  two 
or  even  three?  Does  the  fact  that  a  bird  is  an  all-year  resident 
or  only  a  summer  resident  have  any  influence  in  determining 
its  nesting  time  and  the  number  of  broods  it  rears?  Compare 
the  habits  of  the  various  breeding  species  of  the  locality,  and 
find  out  if  the  summer  residents  have  any  breeding  habits  in 
common  as  distinguished  from  the  all-year  residents. 

Observe  the  behavior  of  the  birds  in  courting  time.  Do  the 
males  have  "singing  contests," as  is  sometimes  reported?  Do 
they  fight  with  each  other?  Do  the  males  or  females  show  any 
differences,  at  this  time,  from  their  more  usual  plumage? 
After  mating  which  bird  selects  the  nesting  site?  Are  old 
nesting  sites  preferred  to  new  ones?  If  two  broods  are  reared 
is  a  new  nest  built  for  the  second  one?  What  are  the  principal 
causes  of  mortality  among  the  eggs  and  young  during  the  breed- 
ing season  ?  What  instincts  or  habits  of  the  parents  have  direct 
reference  to  these  dangerous  conditions?  What  means  of 
protecting  the  nest  are  resorted  to?  What  is  the  behavior  of 
the  parents  toward  enemies  of  the  young? 

Distribution  and  Migration.— The  geographical  distribu- 
tion of  animals  is  a  subject  of  much  importance,  and  offers 
good  opportunities  in  its  more  local  features  for  student  field- 
work.  The  field-study  of  the  birds  of  a  given  locality  will 
comprise  much  observation  bearing  directly  on  zoogeography,  or 
the  distribution  of  animals.  Certain  birds  will  be  found  to 
be  limited  to  certain  parts  of  even  a  small  region;  the  swimmers 
will  be  found  in  ponds  and  streams,  and  the  long-legged  shore 
birds  on  the  pond-  or  stream-banks,  or  in  the  marshes  and 
wet  meadows,  although  a  few,  like  the  upland-plover,  curlews, 
and  godwits  are  common  on  the  dry  upland  pastures.  Dis- 
tinguish the  ground  birds  of  the  shrubs  and  hedge-rows,  and 
these  again  from  the  strictly  forest  birds.  Find  the  special 
haunts  of  swallows  and  king-fishers.  Which  are  the  shy  birds 
driven  constantly  deeper  into  the  wild  places,  or  being  ex- 
terminated by  the  advance  of  man?  Which  birds  do  not  re- 
treat, but  even  find  an  advantage  in  man's  seizure  of  the  land, 
obtaining  food  from  his  fields  and  gardens? 

Make  a  map  on  large  scale  of  the  locality  of  the  school, 


BIRDS  289 

showing  on  it  the  topographic  features  of  the  region,  such  as 
streams,  ponds,  marshes,  hills,  woods,  springs,  wild  pastures, 
etc.,  also  roads  and  paths,  and  such  landmarks  as  school- 
houses,  country  churches,  etc.  On  this  map  indicate  the  local 
distribution  of  the  birds,  as  determined  by  the  data  gradually 
gathered;  mark  favorite  nesting-places  of  various  species, 
roosting-places  of  crows  and  black-birds,  feeding-places,  and 
bathing-  and  drinking-places  of  certain  kinds,  the  exact  spots 
of  finding  rare  visitants,  rare  nests,  etc. 

As  already  mentioned,  many  of  the  birds  of  a  locality  are 
"migrants,"  that  is,  they  breed  farther  north,  but  spend  the 
winter  in  more  southern  latitudes.  These  migrants  pass 
through  the  locality  twice  each  year,  going  north  in  the  spring 
and  south  in  the  autumn.  They  are  much  more  likely  to  be 
observed  during  the  spring  migration  than  in  the  fall,  as  the 
flight  south  is  usually  more  hurried.  The  observation  of  the 
migration  of  birds  is  very  interesting,  and  much  can  be  done 
by  beginning  students.  Notes  should  be  made  recording  the 
first  time  each  spring  a  migrating  species  is  seen,  the  time 
when  it  is  most  abundant,  and  the  last  time  it  is  seen  the  same 
spring.  Similar  records  should  be  made  showing  the  move- 
ments of  the  birds  in  the  fall.  A  series  of  such  records,  cover- 
ing a  few  years,  will  show  which  are  the  earliest  to  appear, 
which  the  later  and  which  the  last.  Such  records  of  appear- 
ance and  disappearance  should  also  be  kept  for  the  summer 
residents,  those  birds  that  come  from  the  south  in  the  spring, 
breed  in  the  locality,  and  then  depart  for  the  south  again  in 
the  autumn.  Notes  on  the  kinds  of  days,  as  stormy,  clear, 
cold,  warm,  etc.,  on  which  the  migration  seems  to  be  most 
active;  on  the  greater  prevalence  of  migratory  flights  by  day 
or  by  night;  on  the  height  from  the  earth  at  which  the  migrants 
fly,  etc.,  are  all  worth  while.  For  an  excellent  simple  account 
of  migration  see  Chapman's  "Bird-Life,"  Chapter  IV.  A 
more  detailed  account  of  migration,  and  one  giving  the  records 
for  many  species  at  many  points  in  the  Mississippi  Valley,  is 
Cooke's  "Bird  Migration  in  the  Mississippi  Valley." 

Plumage. — It  must  be  kept  in  mind  in  using  bird-keys  and 
descriptions  to  determine  species  that  the  descriptions  and 
19 


29o    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

keys  refer  to  adult  birds,  and  in  ordinary  plumage.  Among 
numerous  birds  the  young  of  the  year,  although  old  enough  to 
fly  and  as  large  as  the  adults,  still  differ  considerably  in  plumage 
from  the  latter;  males  differ  from  females,  and  finally  both 
males  and  females  may  change  their  plumage  (hence  color 
and  markings)  with  the  season.  The  seasonal  changes  of 
plumage  accomplished  by  molting  may  be  marked  or  hardly 
noticeable.  "All  birds  get  new  suits  at  least  once  a  year, 
changing  in  the  fall.  Some  change  in  the  spring  also,  either 
partially  or  wholly,  while  others  have  as  many  as  three  changes 
— perhaps,  to  a  slight  extent,  a  few  more.  ...  It  is  claimed 
by  some  that  now  all  new  colors  are  acquired  by  molt,  and  by 
others  that  in  some  instances  (young  hawks)  an  infusion  or 
loss,  as  the  case  may  be,  of  pigment  takes  place  as  the  feather 
forms,  and  continues  so  long  as  it  grows." 

There  is  much  lack  and  uncertainty  of  knowledge  concern- 
ing the  molting  and  change  of  plumage  by  birds,  and  careful 
observations  by  bird  students  should  be  made  on  the  subject. 

For  accounts  of  the  plumage  and  color  of  birds  see  Chapter 
III  in  Chapman's  "Bird-Life"  and  Chapters  VIII  and  IX  in 
Baskett's  "Story  of  the  Birds." 

Structure  and  Habit. — In  connection  with  learning  the  dif- 
ferent kinds  of  birds  in  a  locality,  observations  should  be  made, 
and  notes  of  them  recorded,  on  their  habits,  and  on  their  ex- 
ternal structure  and  its  relation  to  the  habits  of  the  bird. 
The  interesting  adaptation  of  structure  to  special  use  is  particu- 
larly well  shown  in  the  varying  character  of  the  bill  and  feet 
of  birds.  The  various  feeding  habits  and  uses  of  the  feet  of 
different  birds  are  readily  observed,  and  the  accompanying 
modification  of  bills  and  feet  can  be  readily  seen  in  birds  pre- 
served as  "bird-skins."  In  some  cases  the  general  structure 
of  feet  and  bills  may  be  seen  in  the  live  birds  by  the  use  of  an 
opera-glass.  The  characters  of  bills  and  feet  are  much  used 
in  the  classification  of  birds,  so  that  any  knowledge  of  them 
gained  primarily  in  the  study  of  adaptations  will  have  a 
secondary  use  in  classification  work. 

Note  the  foot  of  a  robin,  bluebird,  catbird,  wren,  warbler,  or 
other  Passerine  or  perching  bird.  It  has  three  unwebbed  toes 


BIRDS  291 

in  front  and  a  long  hind  toe  perfectly  opposable  to  the  middle 
front  one.  This  is  the  perching  foot.  Note  the  so-called 
zygodactyl  foot  of  the  woodpecker,  with  two  toes  projecting 
in  front  and  partly  yoked  together,  and  two  similarly  yoked 
projecting  behind.  Note  the  webbed  swimming  foot  of  the 
aquatic  birds;  note  the  different  degrees  of  webbing,  from  the 
toti-palmate,  where  all  four  toes  are  completely  webbed,  pal- 
mate, where  the  three  front  toes  only  are  bound  together  but 
the  web  runs  out  to  the  claws,  to  the  semi-palmate,  where  the 
web  runs  out  only  about  halfway.  Note  the  lobate  foot  of 
the  coots  and  phalaropes.  Note  the  long  slender,  wading 
legs  of  the  sandpipers,  snipe,  and  other  shore-birds;  the  short, 
heavy,  strong  leg  of  the  divers;  the  small  weak  leg  of  the  swifts 
and  humming-birds,  almost  always  on  the  wing;'  the  stout, 
heavily  nailed  foot  of  the  scratchers,  as  the  hens,  grouse,  and 
turkeys;  and  the  strong,  grasping  talons,  with  their  sharp,  long, 
curving  nails,  of  the  hawks  and  owls,  and  other  birds  of  prey. 
In  all  these  cases  the  fitness  of  the  structure  of  the  foot  to  the 
special  habits  of  the  bird  is  apparent. 

Similarly  the  shape  and  structural  character  of  the  bill 
should  be  noted,  as  related  to  its  use,  this  being  chiefly  con- 
cerned of  course  with  the  feeding  habits.  Note  the  strong, 
hooked,  and  dentate  bill  of  the  birds  of  prey ;  they  tear  their 
prey.  Note  the  long,  slender,  sensitive  bill  of  the  sandpipers; 
they  probe  the  wet  sand  for  worms.  Note  the  short,  weak 
bill  and  wide  mouth  of  the  night-hawk  and  whippoorwill, 
and  of  the  swifts  and  swallows;  they  catch  insects  in  this  wide 
mouth  while  on  the  wing.  Note  the  flat,  lamellate  bill  of  the 
ducks;  they  scoop  up  mud  and  water  and  strain  their  food  from 
it.  Note  the  firm,  chisel-like  bill  of  the  woodpeckers;  they 
dig  into  hard  wood  for  insects.  Note  the  peculiarly  crossed 
mandibles  of  the  cross-bills;  they  tear  open  pine  cones  for  seeds. 
Note  the  long,  sharp,  slender  bill  of  the  humming-birds;  they 
get  nectar  and  insects  from  the  bottom  of  flower-cups.  Note 
the  bill  and  foot  of  any  bird  you  examine,  and  see  if  you  can 
recognize  their  special  adaptation  to  the  habits  of  the  bird. 

The  most  casual  observation  of  birds  reveals  differences  in 
the  flight  of  different  kinds  so  characteristic  and  distinctive 


292    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

as  to  give  much  aid  in  determining  the  identity  of  birds  in 
nature.  Note  the  flight  of  the  woodpeckers;  it  identifies 
them  unmistakably  in  the  air.  Note  the  rapid  beating  of  the 
wings  of  quail  and  grouse;  also  of  wild  ducks;  the  slow,  heavy, 
flapping  of  the  larger  hawks  and  owls,  and  of  the  crows;  and 
the  splendid  soaring  of  the  turkey-buzzard  and  of  the  gulls. 
This  soaring  has  been  the  subject  of  much  observation  and 
study,  but  is  still  imperfectly  understood.  The  soaring  bird 
evidently  takes  advantage  of  horizontal  air-currents,  and  some 
observers  maintain  that  upward  currents  also  must  be  present. 
The  speed  of  flight  of  some  birds  is  enormous,  the  passenger- 
pigeon  having  been  estimated  to  attain  a  speed  of  one  hundred 
miles  an  hour.  The  long  distances  covered  in  a  single  continu- 
ous flight  by  certain  birds  are  also  extraordinary,  as  is  also  the 
total  distance  covered  by  some  of  the  migrants.  The  differ- 
ences in  the  structural  character  of  the  wings  should  be  noted 
in  connection  with  the  observation  of  the  differences  in  flight 
habit.  The  tongue  and  tail  of  birds  are  two  other  structures 
the  modifications  and  special  uses  of  which  may  be  readily 
observed  and  studied.  Note  the  structure  and  special  use 
of  the  tongue  and  tail  of  the  woodpeckers;  note  the  tongue 
of  the  humming-bird;  the  tail  of  the  grackles. 

Feeding  Habits,  Economics,  and  Protection  of  Birds. — The 
feeding  habits  of  birds  have  been  already  repeatedly  referred 
to.  The  study  of  these  habits  is  not  only  interesting  but  is, 
of  course,  of  much  importance  in  that  it  is  the  character  of 
these  habits  that  determines  the  economic  relation  of  birds  to 
man,  that  is,  whether  a  particular  bird  species  is  harmful  or 
beneficial.  Casual  observation  shows  that  birds  eat  worms, 
grains,  seeds,  fruits,  insects.  A  single  species  often  is  both 
fruit-eating  and  insect-eating.  Do  fruits  or  do  insects  compose 
the  chief  food- supply  of  the  species?  To  determine  this  more 
than  casual  observation  is  necessary.  The  birds  must  be 
watched  when  feeding  at  different  seasons.  The  most  effec- 
tive determinations  of  the  kind  of  food  taken  by  various 
birds  has  been  based  on  examinations  of  the  stomach  of  many 
individuals  taken  at  various  times  and  localities.  Much 
work  of  this  kind  has  been  done,  especially  by  investigators 


BIRDS  293 

connected  with  the  Bureau  of  Biological  Survey  of  the  United 
States  Department  of  Agriculture,  and  pamphlets  giving  the 
results  of  these  investigations  can  be  had  from  the  Superin- 
tendent of  Public  Documents,  Washington,  D.  C.  The  food 
habits  of  over  400  species  of  native  birds  and  of  several  intro- 
duced kinds  are  referred  to  in  these  publications.  Full  reports 
based  on  stomach  investigations  have  been  made  on  the  food  of 
173  native  species.  As  a  result  of  all  this  work  it  has  been 
clearly  shown  that  a  great  majority  of  birds  are  chiefly  beneficial 
to  man  by  eating  noxious  insects  and  seeds  of  weeds.  Most 
birds  commonly  reputed  to  be  harmful,  and  for  that  reason 
shot  by  farmers  and  fruit-growers,  have  been  proved  to  do 
much  more  good  than  harm.  An  investigation  of  the  food 
habits  of  the  crow,  a  bird  of  ill-repute  among  farmers,  based 
on  an  examination  of  909  stomachs,  show  that  about  29  per 
cent,  of  the  food  of  the  year  consists  of  grain,  of  which  corn 
constitutes  something  more  than  21  per  cent.,  the  greatest 
quantity  being  eaten  in  the  three  winter  months.  All  of  this 
must  be  either  waste  grain  picked  up  in  fields  and  roads,  or 
corn  stolen  from  cribs  and  shocks.  May,  the  month  of 
sprouting  corn,  shows  a  slight  increase  over  the  other  spring 
and  summer  months.  On  the  other  hand,  the  loss  of  grain 
is  off-set  by  the  destruction  of  insects.  These  constitute  more 
than  23  per  cent,  of  the  crow's  yearly  diet,  and  the  larger 
part  of  them  are  noxious.  The  remainder  of  the  crow's  food 
consists  of  wild  fruit,  seeds,  and  various  animal  substances 
which  may  on  the  whole  be  considered  neutral.  However, 
some  few  birds  have  been  proved  to  be,  on  the  whole, 
harmful. 

The  slaughter  of  birds  for  millinery  purposes  has  become  so 
fearful  and  apparent  in  recent  years  that  a  strong  movement 
for  their  protection  has  been  inaugurated.  Rapacious  egg- 
collecting,  legislation  against  birds  wrongly  thought  to  be 
harmful  to  grains  and  fruits,  and  the  selfish  wholesale  killing 
of  birds  by  professional  and  amateur  hunters,  help  in  the  work 
of  destruction.  Apart  from  the  brutality  of  such  slaughter, 
and  the  extermination  of  the  most  beautiful  and  enjoyable 
of  our  animal  companions,  this  destruction  works  strongly 


294    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

against  our  material  interests.  Birds  are  the  natural  enemies 
of  insect  pests,  and  the  destroying  of  the  birds  means  the  rapid 
increase  and  spread,  and  the  enhanced  destructive  power  of 
the  pests.  It  is  asserted  by  investigators  that  during  the  past 
fifteen  years  the  number  of  our  common  song-birds  has  been 
reduced  by  one-fourth.  At  the  present  rate,  says  one  author, 
extermination  of  many  species  will  occur  during  the  lives  of 
most  of  us.  Already  the  passenger-pigeon  and  Carolina  paro- 
quet, only  a  few  years  ago  abundant,  are  practically  exter- 
minated. In  Japan  and  Italy  there  are  hardly  any  song-birds 
left  so  ruthless  has  been  their  destruction.  We  do  not  want 
to  come  to  that  condition.  Protect  the  birds! 


CHAPTER  XXV 
MAMMALS 

Although  by  no  means  the  largest  numerically,  the  class  of 
mammals,  Mammalia,  is  by  far  the  most  important  group  of 
animals.  Not  only  does  it  include  man  himself  but  practically 
all  of  the  domestic  animals  besides  scores  of  others  that  add  to 
his  welfare  by  furnishing  him  food  or  clothing.  The  name 
Mammalia  refers  to  the  mammary  glands  of  the  female  which 
furnish  milk  for  the  nourishment  of  the  young  for  some  time 
after  its  birth. 

In  size,  the  mammals  range  from  the  tiny  pigmy-shrew  of 
fields  and  meadows  to  the  great  wrhales  which  attain  a 
length  of  eighty  to  a  hundred  feet  and  a  weight  of  many  tons. 
In  structure  and  habits  there  is  also  a  remarkable  range  of 
variation.  Most  mammals  live  on  land  and  their  legs  are 
usually  well  fitted  for  walking,  running  or  jumping,  but  some 
live  in  trees  and  have  their  appendages  adapted  for  holding 
on  to  the  branches  or  for  taking  considerable  leaps  through  the 
air.  Others,  like  the  burrowing  gophers  and  moles,  live  in  the 
earth  and  have  the  forelegs  fitted  for  digging.  The  water- 
inhabiting  forms  often  have  their  appendages  modified  into 
fins  or  flippers  and  in  other  ways  show  remarkable  adaptations 
fitting  them  for  their  aquatic  life. 

Body -form  and  Structure. — Most  mammals  are  clothed 
with  hairs,  which  are  peculiarly  modified  epidermal  proc- 
esses. Each  hair,  usually  cylindrical,  is  composed  of  two 
parts,  a  central  pith  containing  air,  and  an  outer  more  solid 
cortex;  each  hair  rises  from  a  short  papilla  sunk  at  the  bottom 
of  a  follicle  lying  in  the  true  skin.  In  some  mammals  the  hairs 
assume  the  form  of  spines,  or  "quills,"  as  in  the  porcupine. 
The  hairy  coat  is  virtually  wanting  in  whales  and  is  very 
sparse  in  certain  other  forms,  the  elephant,  for  example, 

295 


296    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

which  has  its  skin  greatly  thickened.  The  claws  of  beasts  of 
prey,  the  hoofs  of  hoofed  mammals,  and  the  outer  horny 
sheaths  of  the  hollow-horned  ruminants  are  all  epidermal 
structures. 

The  bones  of  mammals  are  firmer  than  those  of  other  ver- 
tebrates, containing  a  larger  proportion  of  salts  of  lime. 
Among  the  different  forms  the  spinal  column  varies  largely  in 
the  number  of  vertebras,  this  variation  being  chiefly  due  to 
differences  in  length  of  tail.  Apart  from  the  caudal  vertebrae 
their  usual  number  is  about  thirty.  The  mammalian  skull 
is  very  firm  and  rigid,  all  the  bones  composing  it,  excepting 
the  lower  jaw,  the  tiny  auditory  ossicles,  and  the  slender 
bones  of  the  hyoid  arch,  being  immovably  articulated.  The 
correspondence  between  the  bones  of  the  two  sets  of  limbs  is 
very  apparent.  The  number  of  digits  varies  in  different  mam- 
mals, and  also  in  the  fore  and  hind  limbs  of  a  single  species. 
Among  the  Ungulates,  or  hoofed  animals,  the  reduction  in  the 
number  of  digits  is  especially  noticeable;  the  forefoot  of  a  pig 
has  four  digits,  that  of  the  cow  two,  and  that  of  the  horse  one. 
The  two  short  "splint"  bones  in  the  horse  are  remnants  of 
lost  digits.  The  teeth  are  important  structures  in  mammals, 
being  used  not  only  for  tearing  and  masticating  food,  but  as 
weapons  of  offense  and  defense.  A  tooth  consists  of  an  inner 
soft  pulp  (in  old  teeth  the  pulp  may  become  converted  into 
bone-like  material)  surrounded  by  hard  white  dentine,  or  ivory, 
which  is  covered  by  a  thin  layer  of  enamel,  the  hardest  tissue 
known  in  the  animal  body.  A  hard  cement  sometimes  covers 
as  a  thin  layer  the  outer  surface  of  the  root,  and  may  also 
cover  the  enamel  of  the  crown.  The  teeth  in  most  forms  are 
of  three  groups :  (a)  the  incisors,  with  sharp  cutting  edges  and 
simple  roots,  situated  in  the  center  of  the  jaw;  (b)  the  canines, 
often  conical  and  sharp-pointed,  next  to  the  incisors;  (c) 
next  the  molars,  broad  and  flat-topped  for  grinding,  and 
divided  into  premolars  and  true  molars.  There  is  great  variety 
in  the  character  and  arrangement  of  the  teeth  in  mam- 
mals, their  variations  being  much  used  in  classification. 

The  mouth  is  bounded  by  fleshy  lips.  On  the  floor  of  the 
mouth  is  the  tongue,  which  bears  the  taste-buds  or  papillae, 


MAMMALS  297 

the  organs  of  taste.  The  esophagus  is  always  a  simple  straight 
tube,  but  the  stomach  varies  greatly,  being  usually  simple,  but 
sometimes,  as  in  the  ruminants  and  whales,  divided  into 
several  distinct  chambers.  The  intestine  in  vegetarian  animals 
is  very  long,  being  in  a  cow  twenty  times  the  length  of  the 
body.  In  the  carnivores  it  is  comparatively  short — in  a  tiger, 
for  example,  but  two  or  three  times  the  length  of  the  body. 

The  blood  of  mammals  is  warm,  having  a  temperature  of 
from  35°  C.  to  40°  C.  (95°  F.  to  104°  F.).  It  is  red  in  color, 
owing  to  the  reddish-yellow,  circular,  non-nucleated  blood- 
corpuscles.  The  circulation  is  double,  the  heart  being  com- 
posed of  two  distinct  auricles  and  two  distinct  ventricles. 
Air  is  taken  in  through  the  nostrils  or  mouth  and  carried 
through  the  windpipe  (trachea)  and  a  pair  of  bronchi  to  the 
lungs,  where  it  gives  up  its  oxygen  to  the  blood,  from  which  it 
takes  up  carbon  dioxide  in  turn.  At  the  upper  end  of  the 
trachea  is  the  larynx,  or  voice-box,  consisting  of  several  car- 
tilages attaching  by  one  end  to  the  vocal  cords  and  by  the 
other  to  the  muscles.  By  the  alteration  of  the  relative  position 
of  these  cartilages  the  cords  can  be  tightened  or  relaxed,  brought 
together  or  moved  apart,  as  required,  to  modulate  the  tone 
and  volume  of  the  voice. 

The  kidneys  of  mammals  are  more  compact  and  definite  in 
form  than  those  of  other  vertebrates.  In  all  mammals  except 
the  Monotremes  (duckbills,  etc.),  they  discharge  their  product 
through  the  paired  ureters  into  a  bladder,  whence  the  urine 
passes  from  the  body  by  a  single  median  urethra.  Mammary 
glands,  secreting  the  milk  by  which  the  young  are  nourished 
during  the  first  period  of  their  existence  after  birth,  are  present 
in  both  sexes  in  all  mammals,  though  usually  functional  in  the 
female  only. 

The  nervous  system  and  the  organs  of  special  sense  reach 
their  highest  development  in  the  mammals.  In  them  the 
brain  is  distinguished  by  its  large  size,  and  by  the  special  pre- 
ponderance of  the  forebrain,  or  cerebral  hemispheres,  over  the 
mid-  and  hind-brain.  Man's  brain  is  many  times  larger  than 
that  of  any  other  known  mammal  of  equal  bulk  of  body,  and 
three  times  as  large  as  that  of  the  largest-brained  ape.  In 


298    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

man  and  the  higher  mammals  the  surface  of  the  forebrain  is 
thrown  into  many  convolutions;  among  the  lowest  the  surface 
is  smooth.  Of  the  organs  of  special  sense,  those  of  touch  con- 
sist of  free  nerve-endings  or  minute  tactile  corpuscles  in  the 
skin.  The  tactile  sense  is  especially  acute  in  certain  regions, 
as  the  lips  and  end  of  the  snout  in  animals  like  hogs,  the  fingers 
in  man,  and  the  under  surface  of  the  tail  in  certain  monkeys. 
All  the  other  sense-organs  are  situated  on  the  head.  The  or- 
gans of  taste  are  certain  so-called  taste-buds  located  in  the 
mucous  membrane  covering  certain  papillae  on  the  surface  of 
the  tongue.  The  organ  of  smell,  absent  only  in  certain  whales, 
consists  of  a  ramification  of  the  olfactory  nerves  over  a  moist 
mucous  membrane  in  the  nose.  The  ears  of  mammals  are 
more  highly  developed  than  those  of  other  vertebrates  both  in 
respect  to  the  greater  complexity  of  the  inner  part  and  the 
size  of  the  outer  part.  A  large  outer  ear  for  collecting  the 
sound-waves  is  present  in  all  but  a  few  mammals.  A  tympanic 
membrane  separates  it  from  the  middle  ear  in  which  is  a  chain 
of  three  tiny  bones  leading  from  the  tympanum  to  the  inner 
ear,  which  is  composed  of  the  three  semi-circular  canals  and 
the  spiral  cochlea.  The  eyes  have  the  structure  characteristic 
of  the  vertebrate  eye,  consisting  of  a  movable  eyeball  com- 
posed of  parts  through  which  the  rays  of  light  are  admitted, 
regulated,  and  concentrated  upon  the  sensitive  expansion, 
called  retina,  of  the  optic  nerve  lining  the  posterior  part  of 
the  ball.  The  eye  is  protected  by  two  movable  lids.  In 
almost  all  mammals  below  the  Primates  (man  and  the 
monkeys)  there  is  a  third  lid,  the  nictitating  membrane.  In 
some  burrowing  rodents  and  others  the  eye  is  quite  vestigial 
and  even  concealed  beneath  the  skin. 

The  mental  qualities  of  animals  reach  their  highest  develop- 
ment among  the  mammals.  In  the  wary  and  patient  hunting 
for  prey  by  the  carnivora,  the  gregarious  and  altruistic  habits 
of  the  herding  hoofed  mammals,,  the  highly  developed  and 
affectionate  care  of  the  young  shown  by  most  mammals,  and 
in  the  loyal  friendship  and  self-sacrifice  of  dogs  and  horses 
in  their  relations  to  man,  we  see  the  culmination  among  animals 
of  the  development  of  the  functions  of  the  nervous  system. 


MAMMALS  299 

In  the  characteristics  of  intelligence  and  reason,  man,  of  course, 
stands  immensely  superior  to  all  other  animals,  but  both  intelli- 
gence and  reason  are  too  often  shown  by  many  of  the  other 
mammals  not  to  make  us  aware  that  man's  mental  powers 
differ  only  in  degree,  not  in  kind,  from  those  of  other  animals. 

Development  and  Life  History. — All  animals  except  the 
Monotremes  give  birth  to  free  young.  The  Monotremes 
produce  their  young  from  eggs  hatched  outside  the  body. 
The  embryo  of  other  mammals  develops  in  the  lower  portion 
of  the  egg-tube,  to  the  walls  of  which  it  is  intimately  connected 
by  a  membrane  called  the  placenta.  (In  the  kangaroos  and 
opossums,  Marsupialia,  there  is  no  placenta.)  Through  this 
placenta  blood-vessels  extend  from  the  body  of  the  mother  and 
from  the  embryo,  and  a  close  connection  between  the  vascular 
systems  of  the  parent  and  the  embryo  thus  becomes  established. 
In  this  way  the  developing  young  derives  its  nourishment  from 
its  mother. 

The  duration  of  gestation  (embryonic  or  prenatal  develop- 
ment in  the  mother's  body)  varies  from  three  weeks  with  the 
mouse,  eight  weeks  with  the  cat,  nine  months  with  the  cow, 
to  twenty  months  with  the  elephant.  Like  the  birds,  the  young 
of  some  mammals,  the  carnivores,  for  example,  are  helpless  at 
birth,  while  those  of  others,  as  the  hoofed  animals,  are  very 
soon  able  to  run  about.  But  all  are  nourished  for  a  longer  or 
shorter  time  by  the  milk  secreted  by  the  mammary  glands  of 
the  mother. 

Classification.1 — The  mammals  are  usually  divided  into 
eleven  orders,  eight  of  which  occur  in  North  America.  The 
small  order  Monotremata  includes  but  three  species  of  primitive 
mammals,  each  representing  a  separate  genus.  They  are 
found  in  Australia,  Tasmania  and  New  Guinea.  Their  most 
unusual  and  primitive  characteristic  is  that  of  laying  eggs. 
After  hatching  from  the  eggs  the  young  are  nourished  on  milk 
which  does  not  issue  from  teats,  but  is  poured  out  over  the 

1  The  classification  adopted  here  is  that  used  by  Hornaday  in  his 
American  Natural  History.  While  later  authorities  have  changed  many 
of  the  scientific  names,  especially  those  of  genera,  the  ones  here  used  are 
the  most  familiar  and  hence  the  most  useful. 


300    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

hair  of  the  abdomen  and  licked  off  by  the  young.  The  duck- 
bill or  platypus,  genus  Ornithorhynchus,  is  about  sixteen  inches 
long,  has  webbed  feet,  close  water-proof  fur,  and  a  flattened 
duck-like  bill.  It  lives  mostly  in  water,  with  an  underground 
chamber  leading  from  the  water,  in  which  the  eggs  are  laid  and 
the  young  reared.  The  spiny  ant-eater,  genus  Echidna,  lives 
in  burrows,  and  feeds,  by  means  of  a  long  snout  bearing  the 
toothless  mouth  and  extensile  tongue,  on  ants.  Its  eggs  are 
carried  in  a  skin  pouch  on  the  abdomen. 

The  order  Marsupialia  includes  the  kangaroos,  opossums, 
and  others.  These  differ  from  all  other  mammals  in  that  the 
female  has  an  external  pouch,  or  marsupium,  in  which  the  young 
are  placed  after  birth  and  carried  about  and  nourished  until 
they  are  more  fully  developed.  As  these  animals  have  no 
placenta,  by  means  of  which  the  young  may  be  nourished  by 
the  blood  of  the  mother,  they  are  born  in  a  very  helpless 
condition  and  so  must  be  cared  for  in  the  marsupium  for  some 
months.  In  Australia  most  of  the  land  animals  are  marsupials. 
The  kangaroos  are  the  most  familiar  examples.  They  were 
formerly  quite  abundant,  but  have  been  hunted  for  their  skins 
to  make  leather  for  shoes  until  their  numbers  have  been  much 
reduced.  The  opossum,  Didelphys  virginiana,  which  is  the 
only  North  American  representative  of  the  order,  lives  in  trees, 
is  about  the  size  of  a  common  cat,  and  has  a  dirty-yellowish 
woolly  fur.  Its  tail  is  long  and  scaly,  like  a  rat's.  Its  food 
consists  chiefly  of  insects,  although  small  reptiles,  birds,  and 
bird's  eggs  are  often  eaten.  When  ready  to  bear  young  the 
opossum  makes  a  nest  of  dried  grass  in  the  hollow  of  a  tree, 
and  produces  about  thirteen  very  small  (half  an  inch  long) 
helpless  creatures.  These  are  then  placed  by  the  mother  in 
her  pouch.  Here  they  remain  until  two  months  or  more  after 
birth.  Probably  all  the  North  American  opossums  found  from 
New  York  to  California  and  especially  common  in  the  Southern 
States,  belong  to  a  single  species,  but  there  is  much  variety 
among  the  individuals.  They  are  commonly  used  for  food 
and  are  sometimes  seen  on  the  market. 

The  order  Edentata  includes  the  sloths,  armadillos  and  ant- 
eaters,  all  found  in  tropical  regions.  The  sloths  dwell  in  the 


MAMMALS  301 

tree  tops  feeding  on  green  leaves.  They  are  not  entirely  tooth- 
less as  the  name  of  the  order  would  indicate,  but  they  are 
nearly  so.  "One  cannot  look  at  a  live  sloth  without  thinking 
that  nature  has  but  poorly  equipped  this  animal  to  live  in  this 
murderous  world.  Its  countenance  is  a  picture  of  complete  and 
far-reaching  stupidity,  its  bodily  form  the  acme  of  four-footed 
helplessness.  It  can  neither  fight,  hide,  nor  run  away.  It  has 
no  defensive  armor,  not  even  spines.  It  is  too  large  to  live  in  a 
hole  in  a  tree,  and  too  weak  to  dig  a  burrow  in  the  earth.  It 
is  too  tired  to  walk  on  its  feet,  as  the  monkeys  do,  so  through- 
out its  queer  life  it  hangs  underneath  the  branches  of  the  trees 
in  which  it  finds  its  food."  (Hornaday.) 

The  armadillos  occur  principally  in  South  America,  but  one 
species,  the  nine-banded  armadillo,  Tatu  novemcinctum,  is 
found  also  in  Mexico,  Texas  and  Arizona.  They  are  covered 
with  hard  bony  plates  which  form  a  protecting  case  for  all 
parts  of  the  body.  When  attacked  the  animal  draws  in  its 
legs  and  rolls  up  into  a  ball  leaving  exposed  to  its  enemy  only 
this  bony  shell. 

The  ant-eaters  are  also  confined  to  South  and  Central 
America.  The  small  mouth  situated  at  the  end  of  a  long 
slender  beak  is  entirely  toothless.  They  devour  great  quan- 
tities of  ants  and  thus  help  to  reduce  the  numbers  of  these 
insects  which  are  often  great  pests  in  tropical  countries. 

To  the  order  Sirenia  belong  the  manatees,  or  sea-cows,  and 
the  dugongs.  These  are  aquatic,  seal-like  animals  with  the 
fore  legs  reduced  to  a  pair  of  flippers  and  the  hind  legs  wanting. 
One  species  of  manatee,  Trichechus  latirostris,  is  still  found  off 
Florida,  and  others  occur  in  the  warm  waters  of  the  islands  and 
along  the  coast  of  Mexico,  Central  and  South  America.  The 
great  Arctic  sea-cow,  Hydrodamalis  gigas,  once  occurred 
abundantly  in  the  Bering  Sea  region  where  it  reached  a  length 
of  twenty  to  thirty  feet.  The  natives  and  the  whalers  used 
it  for  food  until  it  was  practically  exterminated  about  1780. 
The  last  animal  of  this  species  seen  was  killed  in  1854. 

The  Cete  are  an  order  of  aquatic  mammals  all  more  or  less 
fish-like.  The  whales,  dolphins  and  porpoises  belong  to  this 
order.  In  all,  the  posterior  limbs  are  so  reduced  that  they 


302    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

do  not  appear  at  all  externally,  while  the  forelimbs  are  devel- 
oped as  broad  flattened  paddles  without  distinct  fingers  or  nails. 
The  tail  ends  in  a  broad  horizontal  fin  or  paddle.  The  Cete 
are  all  predaceous,  fish,  pelagic  crustaceans,  and  especially 
squids  and  cuttle-fishes  forming  their  principal  food.  Most 
of  the  species  are  gregarious,  the  individuals  swimming  together 
in  "schools."  Some  of  them  can  remain  under  water  for  a 
long  while  but  they  must  all  come  to  the  surface  to  breathe. 
As  the  whales  come  to  the  surface  they  blow  the  air  from  their 
lungs  out  through  the  blow  holes  on  top  of  their  head.  This 
air  is  so  heavily  laden  with  moisture  that  it  is  usually  supposed 
and  said  that  the  whale  is  actually  "spouting"  water. 

The  whales  comprise  two  families,  the  sperm  whales,  Physe- 
terida,  with  numerous  teeth  in  their  lower  jaw,  and  the  whale- 
bone whales,  Balanidce,  which  have  in  the  mouth,  instead  of 
teeth,  many  long  parallel  plates  with  fringed  edges,  the  valuable 
"whalebone"  of  commerce.  The  great  sperm  whales  reach  a 
length  of  eighty  feet  of  which  the  head  forms  nearly  one-third. 
They  feed  on  various  kinds  of  fish  and  squid.  They  are  hunted 
for  the  sperm  oil,  which  is  obtained  from  the  "blubber  or  layer  of 
fat  that  lies  under  the  skin,  and  for  the  spermaceti  which  is 
obtained  from  the  head  and  is  used  in  making  candles  and 
ointments.  The  teeth  of  these  whales  are  also  of  considerable 
value,  being  used  for  ivory.  Of  the  whalebone  whales,  the 
sulphur-bottom  whale  of  the  Pacific  Ocean,  reaching  a  length 
of  nearly  one  hundred  feet,  is  the  largest,  and  hence  the  largest 
of  all  living  animals.  These  great  monsters  feed  on  minute 
shrimp-like  crustaceans  and  other  small  organisms  swimming 
at  or  near  the  surface  of  the  sea.  The  whale  swims  along 
with  its  mouth  wide  open,  the  mass  of  "whalebone"  plates 
acting  as  a  strainer  until  a  mouthful  of  dainty  food  is  procured. 
The  sulphur-bottom  whale,  the  right  whale,  the  hump-back 
whale,  the  bow-head  whale  and  others  are  all  hunted  for  the 
"whalebone,"  or  baleen,  and  for  the  oil.  The  bow-head  or 
polar  whale  is  the  most  important  commercially,  a  single  speci- 
men sometimes  yielding  3500  pounds  of  whalebone  and  275 
barrels  of  oil. 

The  family  Delphinidce  includes  the  dolphins  and  porpoises 


MAMMALS  303 

and  certain  others  some  of  which  yield  valuable  oil.  It  also 
includes  the  vicious  killer  "whale,"  or  orca,  which  "has  the 
appetite  of  a  hog,  the  cruelty  of  a  wolf,  the  courage  of  a  bulldog, 
and  the  most  terrible  jaws  afloat."  Although  they  are  not 
more  than  fifteen  to  twenty  feet  long  three  or  four  of  them 
will  attack  and  destroy  even  the  largest  whale. 

The  hoofed  mammals,  order  Ungulata,  include  some  of  the 
most  familiar  mammal  forms.  Most  of  the  domestic  animals, 
as  the  horse,  cow,  hog,  sheep  and  goat,  belong  to  this  order,  as 
well  as  the  familiar  deer,  antelope,  and  buffalo  of  our  own  land, 
and  elephant,  rhinoceros,  hippopotamus,  giraffe,  camel,  zebra, 
etc.,  familiar  in  zoological  gardens  and  menageries.  The  order 
is  a  large  one,  its  members  being  characterized  by  the  presence 
of  from  one  to  four  hoofs,  which  are  the  enlarged  and  thick- 
ened claws  of  the  toes.  The  Ungulates  are  all  herbivorous, 
and  have  their  molar  teeth  fitted  for  grinding,  the  canines  being 
absent  or  small.  The  order  is  divided  into  the  Perissodactyla, 
or  odd-toed  forms,  like  the  horse,  zebra,  tapir,  and  rhinoceros, 
the  Artiodactyla,  or  even- toed  forms,  like  the  oxen,  sheep,  deer, 
camels,  pigs  and  hippopotami,  and  the  Proboscidia,  the  ele- 
phants. The  Artiodactyls  comprise  two  groups,  the  Ruminants 
and  Non-ruminants.  All  the  native  Ungulata  of  our  Northern 
States  belong  to  the  Ruminants,  so-called  because  of  their  habit 
of  chewing  a  cud.  A  ruminant  first  presses  its  food  into  a  ball, 
swallows  it  into  a  particular  one  of  the  divisions  of  its  four- 
chambered  stomach,  and  later  regurgitates  it  into  the  mouth, 
thoroughly  masticates  it,  and  swallows  it  again,  but  into 
another  stomach-chamber.  From  this  it  passes  through  the 
other  two  chambers  into  the  intestine. 

The  deer  family,  Cervida,  comprises  the  familiar  Virginia,  or 
red,  deer  of  the  Eastern  and  Central  States  and  the  white- 
tailed,  black-tailed,  and  mule  deers  of  the  West,  all  belonging 
to  the  genus  Odocoileus,  the  great  antlered  elk  or  wapiti, 
Cervus  canadensis,  the  great  moose,  Alee  americana,  largest  of 
the  deer  family,  and  the  American  reindeer  or  caribou,  Rang- 
ifer  caribou.  All  species  of  the  Cervidae  have  solid  horns,  more 
or  less  branched,  which  are  shed  annually.  Only  the  males 
(except  with  the  reindeer)  have  horns.  The  antelope,  Antilo- 


3o4    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

capra  americana,  common  on  the  Western  plains,  also  sheds  its 
horns,  which,  however,  are  not  solid  and  do  not  break  off  at  the 
base  as  in  the  deer,  but  are  composed  of  an  inner  bony  core 
and  an  outer  horny  sheath,  the  outer  sheath  only  being  shed. 
The  family  Bovidce  includes  the  once-abundant  buffalo,  or  bison, 
Bison  bison,  the  big-horn,  or  Rocky  Mountain  sheep,  Oms 
canadensis,  and  the  strange  pure  white  Rocky  Mountain  goat, 
Oreamnos  montanus.  The  buffalo  was  once  abundant  on  the 


FIG.  132. — Buffalo,  Bison  bison,  in  Golden  Gate  Park,  San  Francisco,  Cal. 


Western  plains,  travelling  in  enormous  herds.  But  so  relent- 
lessly has  this  fine  animal  been  hunted  for  its  skin  and  flesh  that 
it  is  now  practically  exterminated.  A  small  herd  is  still  to  be 
found  in  Yellowstone  Park,  another  in  Canada,  and  other  pro- 
tected groups  live  in  parks  and  zoological  gardens.  On  Jan.  i, 
1913,  a  total  of  3,453  bison  were  alive  in  North  America.  In 
all  of  the  Bovidce  the  horns  are  simple,  hollow,  and  permanent, 
each  enclosing  a  bony  core. 

Many  of  these  native,  wild  hoofed  animals  have  been  impor- 


MAMMALS 


305 


tant  as  a  source  of  food,  but  nearly  all  are  now  so  reduced  in 
numbers  that  they  are  little  hunted  except  for  sport.  The 
domesticated  mammals,  the  most  important  of  which  belong 
to  this  order,  are  discussed  in  Chapter  XXVI. 

The  order  Glires,  the  rodents,  or  gnawers,  is  the  largest  of  the 
orders  of  mammals,   and  includes   the  rabbits,   porcupines, 


FIG.  133. — A  buffalo,  Bison  bison,  killed  for  its  skin  and  tongue,  on  the 
plains  of  western  Kansas,  forty  years  ago.  (Photograph  by  J.  L.  Knight.) 

gophers,  chipmunks,  beavers,  squirrels,  rats  and  mice.  The 
special  arrangement  and  character  of  the  teeth  are  character- 
istic of  this  order.  There  are  no  canines,  a  toothless  space 
being  left  between  the  incisors  and  molars  on  each  side.  There 
are  only  two  incisor  teeth  in  each  jaw  (rarely  four  in  the  upper 
jaw).  These  teeth  grow  continuously  and  are  kept  sharp 
and  of  uniform  length  by  the  gnawing  on  hard  substances  and 


3o6    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  constant  rubbing  on  each  other.     The  food  of  rodents  is 
chiefly  vegetable. 

The  order  is  divided  into  several  families  of  which  the  fol- 
lowing are  the  most  common:  the  Leporida,  the  rabbits  and 
hares;  the  Erethizontida,  the  porcupines;  the  Geomyida,  the 


FIG.  134. — Chipmunk.     (Permission  of  Camera  Craft.) 

pocket  gophers;  the  Zapodidce,  the  jumping  mice;  the  Dipodida, 
the  pocket  mice  and  kangaroo  rats;  the  Murida,  the  mice  and 
rats;  the  Castorida,  the  beavers;  and  the  Sciurida,  the  squir- 
rels, woodchucks  and  prairie-dogs. 

Of  the  hares  and  rabbits,  the  cottontail,  Lepus  sylvaticus,  and 


MAMMALS  307 

the  common  jack-rabbit,  L.  texanus,  are  the  best  known. 
The  cottontail  is  found  all  over  the  United  States,  but  shows 
some  variation  in  the  different  regions.  There  are  several 
species  of  jack-rabbits,  all  limited  to  the  plains  and  mountain 
regions  west  of  the  Mississippi  river.  The  food  of  rabbits  is 
strictly  vegetable,  consisting  of  succulent  roots,  branches,  or 
leaves. 

As  long  as  they  confine  their  feeding  to  wild  plants,  or  even 
to  cultivated  field  crops,  the  damage  that  they  do  is  usually 
not  great,  although  when  very  abundant  they  may  materially 
injure  wheat  or  alfalfa  fields.  In  the  gardens,  however,  where 
they  will  attack  all  kinds  of  vegetables,  they  sometimes  cause 
considerable  annoyance,  or  even  serious  loss.  Tree  and  shrubs 
are  often  injured,  especially  in  the  winter  time  when  the  ground 
is  covered  with  snow  and  there  is  little  other  green  food  to  be 
had.  The  rabbits  eat  the  ends  of  the  branches  within  their 
reach  or  gnaw  the  bark,  sometimes  girdling  the  tree.  The  most 
satisfactory  remedy,  where  the  rabbits  are  abundant  enough  to 
be  a  nuisance,  is  to  allow  hunters  to  kill  them.  Most  rabbits 
are  of  fine  flavor,  especially  when  young.  The  cotton-tails  are 
usually  considered  superior  even  to  Belgian  hares  and  other 
domesticated  species.  In  some  regions  where  the  country  is 
sufficiently  open  "rabbit  drives"  are  organized,  and  as  many 
as  10,000  to  20,000  rabbits  are  killed  in  a  single  drive. 
Various  kinds  of  traps  are  used  in  the  orchards  and  gardens, 
and  poisoning  is  sometimes  resorted  to,  but  the  latter  is  always 
dangerous.  Rabbit-proof  fences  are  effective  and  although 
expensive  are  often  profitable.  Trees  may  be  protected  with 
close  meshed  wire  or  by  veneer,  cornstalks,  sacking  or  other 
substances.  Most  of  thepaints  or  smears  usually  recommended 
to  be  put  on  the  trees  are  apt  to  injure  them.  The  sulphur- 
lime  mixture,  such  as  is  used  for  scale  insects  (see  page  415) 
has  proved  a  very  effective  repellent  wash  in  many  places. 

Nearly  fifty  years  ago  the  common  rabbit  of  Europe  was 
introduced  into  Australia  as  a  game  animal.  In  the  absence 
of  their  natural  enemies  the  rabbits  multiplied  so  rapidly  that 
they  soon  became  serious  pests  and  have  cost  the  country 
millions  of  dollars,  $3,500,000  being  the  estimated  annual  loss. 


3o8    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  skins  are  shipped  in  great  quantities  to  Europe,  where  the 
fur  is  used  in  making  many  articles  such  as  boas,  muffs,  hats 
and  trimmings.  The  fur  of  the  American  rabbits  is  but  little 
used  except  by  the  Indians. 

There  are  two  North  American  species  of  porcupines,  an 
Eastern  one,  Erethizon  dorsatus,  and  a  Western  one,  E.  epixan- 
thus.  The  quills  in  both  these  species  are  short,  being  only  an 
inch  or  two  in  length,  and  are  barbed.  In  some  foreign  porcu- 
pines they  are  a  foot  long.  They  are  loosely  attached  in  the 
skin  and  may  be  readily  pulled  out,  but  they  cannot,  be  shot 
out  by  the  porcupine,  as  is  popularly  told.  The  little  guinea- 
pigs,  Cavia,  kept  as  pets,  are  South  American  animals  related 
to  the  porcupines.  Because  of  the  ease  with  which  they  can 
be  reared  and  handled,  and  for  certain  technical  reasons,  guinea- 
pigs  are  much  used  in  physiological  and  bacteriological  labora- 
tories for  experimental  purposes.  The  sacrifice  in  this  way  of  a 
few  thousand  guinea-pigs  has  aided  in  enormously  increasing  our 
knowledge  of  the  causes  of  and  remedies  for  infectious  disease. 

The  pocket-gophers,  of  which  there  are  several  genera  and 
species  mostly  inhabiting  the  central  plains,  are  rodents  found 
only  in  North  America.  They  all  live  underground,  making 
extensive  galleries.  They  are  very  destructive  to  such  crops  as 
alfalfa,  clover,  grains,  potatoes,  and  to  many  others,  and  often 
cause  the  loss  of  thousands  of  dollars  in  orchards  by  destroying 
the  roots  or  girdling  the  trees  and  thus  quickly  killing  them. 
Gophers  may  be  poisoned  or  trapped.  Small  bits  of  carrots, 
potatoes,  raisins,  prunes  or  other  substances  may  be  poisoned 
by  placing  a  small  amount  of  strychnine  in  them;  an  amount 
equal  to  about  half  a  grain  of  wheat  is  sufficient.  The  poisoned 
baits  should  be  placed  in  the  main  tunnel,  not  in  the  short 
lateral  tunnels  that  are  used  for  bringing  the  dirt  to  the  surface. 
If  placed  in  the  lateral  tunnels  they  may  be  covered  over  or 
pushed  to  the  surface  where  other  animals  or  birds  may  find 
them.  Many  special  forms  of  traps  are  used,  almost  all  of 
them  good  if  sufficient  care  is  taken  in  setting  them.  When 
the  ground  is  not  too  dry  success  may  often  attend  the  use  of 
carbon  bisulphide.  Rags  or  waste  may  be  saturated  with  this 
liquid  and  placed  in  the  hole  which  is  then  closed  tightly,  or 


MAMMALS  309 

the  gas  may  be  introduced  by  means  of  a  small  hand  pump 
constructed  for  this  purpose. 

The  mice  and  rats  constitute  a  large  family  of  which  the 
house  mice  and  rats,  the  various  field  mice,  the  wood-rat, 
Neotoma  pennsylvanica,  and  the  muskrat,  Fiber  zibethicus,  are 
familiar  representatives.  The  common  brown  rat,  Mus  decu- 
manus,  was  introduced  into  this  country  from  Europe  about 
1775,  and  has  now  nearly  wholly  supplanted  the  black  rat,  M. 
ralttis,  also  a  European  species,  introduced  about  1544.  Rats 
are  by  far  the  worst  of  all  the  mammalian  pests.  The  damage 
that  they  do  to  foods  and  stored  products  the  world  over 
amounts  to  hundreds  of  millions  of  dollars  annually  and,  what 
is  far  worse,  they  may  carry,  as  we  shall  learn  (page  375),  the 
germs  of  the  dreaded  bubonic  plague  and  are  thus  a  constant 
menace.  The  fight  against  them  has  been  carried  on  for  ages 
and  still  they  continue  to  multiply  and  spread.  Poison  and 
traps  are  more  or  less  successful,  the  degree  of  success  depend- 
ing, in  a  large  measure,  on  the  skill  of  the  one  who  is  doing  the 
poisoning  or  the  trapping  and  to  a  still  greater  extent  on  the 
age  or  experience  of  the  rats,  the  old,  experienced  fellows  be- 
coming very  cunning.  The  modern  methods  of  fighting  the 
rat  are  to  cut  off  its  food  supply  and  to  destroy,  as  far  as  possi- 
ble, its  breeding  places.  A  liberal  supply  of  food  means  many 
litters  of  rats  and  many  young  in  a  litter.  Scarcity  of  food  will 
reduce  both,  so  if  garbage  cans  are  kept  closed  and  feed  bins 
and  cellars  and  store  houses  made  rat  proof,  the  rats  will 
either  die  or  seek  a  more  hospitable  place.  The  great  fight 
carried  on  against  the  rats  in  San  Francisco  when  this  city 
successfully  fought  the  plague  some  years  ago,  shows  what 
can  be  done  by  united  effort  directed  along  these  lines.  In 
that  fight  fully  1,000,000  rats  were  slain,  8,000,000  square 
feet  of  concrete  were  used  in  rat-proofing,  more  than  100,000 
new,  covered  garbage  cans  were  installed,  and  all  rubbish  was 
cleaned  up  in  all  parts  of  the  city.  It  was  the  rat  fighting 
that  stayed  the  disease. 

The  muskrat,  Fiber  spp.,  is  one  of  our  largest  rats,  reaching  a 
length  of  twenty-one  inches.  It  lives  in  the  water,  and  makes 
houses  there  much  as  do  beavers,  and  is  hunted  for  its  fur. 


3io  ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Mice,  as  a  rule,  are  less  serious  pests  than  rats,  but  the  total 
damage  that  the  common  house  mouse,  M us  musculus,  does 
about  dwellings  and  storehouses  is  very  great.  This  species 
is  a  native  of  India,  but  has  become  thoroughly  cosmopolitan. 
Some  of  the  field  mice,  Microtus  sp.,  frequently  do  considerable 
damage  in  fields  of  alfalfa  or  grain  and  in  nurseries  and  orchards. 
It  is  estimated  that  the  damage  that  they  do  in  the  United 
States  amounts  to  more  than  $3,000,000  annually.  Rarely 
they  occur  in  great  numbers  and  thus  become  a  veritable 
plague,  devastating  large  areas.  In  such  outbreaks  they  are 
best  controlled  by  placing  alfalfa  or  grain  poisoned  by  arsenic 
in  or  at  the  entrance  of  their  burrows.  These  plagues  rarely 
last  more  than  a  season,  as  natural  enemies  and  diseases  soon 
reduce  the  mice  to  normal  numbers. 

The  beaver,  Castor  canadensis,  is  the  largest  rodent,  weigh- 
ing sometimes  as  much  as  fifty  pounds.  With  their  sharp 
chisel-like  teeth  beavers  cut  down  small  trees  in  order  that  they 
may  get  at  the  bark  which  they  use  for  food.  They  often 
build  dams  of  considerable  size  in  order  to  make  a  deep  pond 
in  which  to  live  and  work.  The  dam  is  made  of  trees  which 
have  fallen  into  the  stream  and  sticks  of  wood  of  all  sizes  with 
the  interstices  filled  with  mud.  The  beavers  burrow  into  the 
banks  or  build  houses  which  extend  above  the  surface  of  the 
water.  The  entrance  to  the  burrow  is  always  below  the  surface. 
Beavers  are  much  hunted  for  their  fur,  which  is  very  valuable. 
They  are  so  nearly  exterminated  that  they  are  now  found  only 
in  a  few  localities. 

The  woodchucks,  or  ground-hogs,  Marmolla  spp.,  are  other 
familiar  rodents  larger  than  most  members  of  the  order.  The 
chip-munks  and  ground-squirrels,  of  which  there  are  several  gen- 
era, are  commonly  known  rodents  found  all  over  the  country. 
They  are  the  terrestrial  members  of  the  squirrel  family,  the 
best  known  arboreal  members  of  which  are  the  red  squirrel, 
Sciurus  hudsonicus,  the  fox-squirrels,  S.  ludovicianus  and  S. 
niger,  and  the  gray  or  black  squirrel,  S.  carolinensis.  The 
little  flying  squirrel,  Sciuropterus  volans,  is  abundant  in  the 
eastern  states. 

The   ground-squirrels,  commonly    known  as  spermophiles 


MAMMALS  311 

because  they  are  so  fond  of  seeds,  are  very  serious  pests  of 
grain  growers  in  many  regions.  The  remedies  for  them  are  the 
same  as  for  gophers,  that  is,  carbon  bisulphide  put  into  the  holes 
when  the  ground  is  moist,  or  poisoned  grain  put  at  the  entrance 
to  the  burrows.  One  of  the  western  members  of  the  group 
has  been  found  to  be  affected  at  times  with  the  plague  bacillus, 
and  instances  are  recorded  where  human  beings  have  become 
infected  with  this  disease  after  being  bitten  by  fleas  from 
plague-infected  ground-squirrels.  Some  of  the  ground-squir- 
rels compensate  in  a  measure  for  the  damage  that  they  do, 
by  eating  many  destructive  insects  such  as  grasshoppers, 
cut-worms,  beetles,  etc.,  often,  too,  killing  mice  and  other 
small  noxious  animals.  The  thirteen-lined  spermophile, 
Citellus  tridecemilineatus ,  is  common  over  the  Mississippi 
valley,  and  other  large  members  of  the  same  genus  occur 
throughout  the  West.  The  prairie-dogs,  Cynomys  ludovicianus, 
are  closely  related  to  the  ground-squirrels,  and  are  found  in 
great  "towns"  over  the  western  plains.  Lands  so  infested 
are  unfit  for  cultivation  and  may  even  be  ruined  for  pasture. 
Wheat  or  other  grain  poisoned  with  strychnine  placed  at  the 
entrance  to  their  burrows  in  the  winter  or  early  spring  will 
kill  most  of  them.  Carbon  bisulphide,  as  recommended  for 
gophers  and  squirrels,  is  very  effective. 

The  shrews  and  moles  belong  to  the  order  Insectivora,  They 
are  all  small  carnivorous  animals,  which,  because  of  their  size, 
confine  their  attacks  chiefly  to  insects.  The  shrews  are  small 
and  mouse-like;  certain  kinds  of  them  lead  a  semi-aquatic  life. 
There  are  nearly  a  score  of  species  in  North  America.  Of  the 
moles,  of  which  there  are  but  few  species,  the  common  mole, 
Scalops  aquaticus,  is  well  known,  while  the  star-nosed  mole, 
Condylura  cristata,  is  recognizable  by  the  peculiar  rosette  of 
about  twenty  cartilaginous  rays  at  the  tip  of  its  snout.  Moles 
live  underground,  and  have  the  fore  feet  wide  and  shovel-like 
for  digging.  As  they  destroy  great  numbers  of  cutworms,  grubs 
and  other  injurious  insect  larvae  and  do  not  eat  vegetable  food 
they  must  be  regarded  as  very  beneficial.  But  their  burrows 
are  sometimes  so  destructive  in  the  lawns  and  flower  beds  that 


3i2    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  damage  they  do  more  than  counterbalances  the  good.  In 
the  fields  and  garden,  however,  they  should  be  protected. 

The  bats,  order  Chiroptera,  differ  from  all  other  mammals  in 
having  the  fore  limbs  modified  for  flight  by  the  elongation  of 
the  forearms  and  especially  of  four  of  the  fingers,  all  of  which 
are  connected  by  a  thin  leathery  membrane  which  includes  also 
the  hind  feet  and  usually  the  tail.  Bats  are  chiefly  nocturnal, 
hanging  head  downward  by  their  hind  claws  in  caves,  hollow 
trees,  or  dark  rooms  through  the  day.  They  feed  chiefly  on 
insects,  although  some  foreign  kinds  live  on  fruits.  There 
are  a  dozen  or  more  species  of  bats  in  North  America,  the  most 
abundant  kinds  in  the  Eastern  States  being  the  little  brown 
bat,  Myotis  subulatus,  about  three  inches  long  with  small 
fox-like  face,  high  slender  ears,  and  a  uniform  dull  olive-brown 
color,  and  the  red  bat,  Lasiurus  borealis,  nearly  four  inches  long, 
covered  with  long,  silky,  reddish-brown  fur,  mostly  white  at 
tips  of  the  hairs.  Most  of  the  bats  are  beneficial  as  they  cap- 
ture and  destroy  many  insects,  but  a  few  exotic  kinds  feed  on 
fruit,  and  the  large  vampire  bats  suck  the  blood  of  other 
animals. 

The  order  Ferce  include  all  those  animals  usually  called  the 
carnivora,  such  as  the  lions,  tigers,  cats,  wolves,  dogs,  bears, 
panthers,  foxes,  weasels,  seals,  etc.  All  of  them  feed  chiefly  on 
animal  substance  and  are  predatory,  pursuing  and  killing  their 
prey.  They  are  mostly  fur  covered  and  many  are  hunted  for 
their  skin.  They  have  never  less  than  four  toes,  which  are 
provided  with  strong  claws  that  are  frequently  more  or  less 
retractile.  The  canine  teeth  are  usually  large,  curved,  and 
pointed. 

The  FelidcB,  or  cat  family,  includes  the  lions,  tigers,  hyenas, 
leopards,  jaguars,  panthers,  wild  cats,  lynxes,  and  the  common 
domestic  cat.  The  largest  of  them,  the  lions,  occur  in  Central 
Africa  preying  on  any  other  animals  that  they  can  capture. 
Inferior  to  lions  in  size  but  superior  in  strength  are  the  Bengal 
tigers  that  occur  throughout  the  jungles  of  southern  Asia. 
Other  smaller  tigers  occur  in  other  parts  of  the  Old  World. 
They  often  prey  upon  domestic  animals  and  sometimes  will 
even  attack  man  if  enraged  or  driven  by  hunger.  Indeed,  there 


MAMMALS  313 

is  a  notable  annual  loss  of  life  among  the  natives  of  India  from 
the  attacks  of  "man-eating"  tigers. 

The  jaguar,  Fdis  onca,  which  occurs  as  far  north  as  the 
southern  part  of  the  United  States,  is  the  largest  and  most 
beautiful  of  the  American  members  of  this  family.  The  puma, 
or  mountain  lion,  or  cougar,  Fells  concolor,  occurs  throughout 
the  western  mountains  and  foothills.  It  preys  upon  deer, 
mountain  sheep  and  other  wild  animals,  and  sometimes  upon 
domestic  animals.  Like  all  members  of  the  family  it  will 
avoid  man  if  possible,  but  in  defense  of  self  or  of  young  and 
sometimes  when  driven  by  hunger,  the  pumas  will  attack  man 
savagely.  Large  specimens  measure  five  feet  in  length  from 
nose  to  base  of  tail. 

The  Canada  lynx,  Lynx  canadensls,  and  the  bay  lynx,  wrhich 
is  also  known  as  the  red  lynx,  or  wild  cat,  or  bob  cat,  Lynx  rufus, 
still  occurs  in  considerable  numbers  in  many  parts  of  the  coun- 
try, often  raiding  the  poultry  yards.  The  ocelots,  Fells  parda- 
lis,  beautifully  marked  by  spots  and  broken  bands  running 
lengthwise  of  the  body,  occur  only  as  far  north  as  Texas. 

The  Canida,  or  dog  family,  includes  the  wolves,  coyotes, 
foxes,  and  the  domestic  dogs.  The  gray  or  timber  wolf,  Cams 
occidentalis,  is  the  largest  and  most  formidable  of  them.  These 
wolves  range  through  the  north  and  west  where  they  often 
hunt  in  packs  and  are  able  to  overpower  animals  much  larger 
than  themselves.  They  were  formerly  very  troublesome  on 
stock  ranches,  killing  many  young  calves  and  colts.  The  coyote, 
or  prairie  wolf,  Canis  latrans,  is  only  about  two-thirds  as  large 
as  the  gray  wolf.  It  feeds  on  small  animals  and  birds,  and 
often  visits  the  ranchers'  poultry  yards.  But  as  coyotes  often 
kill  prairie-dogs  and  ground-squirrels  they  make  recompense  in 
some  measure  for  the  damage  that  they  do.  They  are  usually 
crafty  enough  to  avoid  all  traps  and  to  keep  out  of  range  of  guns. 
Wolves  and  coyotes  are  sometimes  destroyed  by  placing  a  two 
to  four  grain  capsule  filled  with  strychnine  in  small  pieces  of 
beef  or  suet.  The  meat  should  not  be  touched  by  the  hands, 
and  should  be  dropped  from  horseback  along  trails  used  by 
the  wolves. 

There  are  many  species  of  foxes  in  America,  the  red  fox, 


3i4    ECONOMIC  ZOOLOGY  AND   ENTOMOLOGY 

Vulpes  fulvus,  being  perhaps  the  most  widely  distributed  and 
generally  known.  The  black  fox,  or  the  silver  gray  fox,  is  a 
variety  of  the  red  fox  that  is  wholly  black  except  the  tip  of  the 
tail,  which  is  white.  These  are  the  most  valuable  for  fur, 
single  skins  selling  at  from  $500  to  $1000,  and  extra  fine  ones 
sometimes  bringing  $2000  to  $2500.  The  Arctic  fox,  Vulpes 
lagopus,  is  white  all  the  year  around  in  its  northern  range,  but 
further  south  it  is  darker  and  is  known  as  the  blue  fox.  The 
white  skins  are  worth  $10  to  $12,  the  blue  skins  two  to  four 
times  as  much.  In  Alaska  successful  attempts  have  been  made 
to  rear  these  foxes  in  captivity.  Less  success  has  so  far  re- 
warded the  efforts  to  breed  the  black  or  silver  fox,  as  it  is  much 
more  shy  and  must  have  game  for  its  food,  refusing  to  take  the 
food  prepared  for  it  as  does  the  blue  fox.  Doubtless,  however, 
further  experiments  will  show  how  it  may  be  handled  and 
bred  successfully  in  large  restricted  areas. 

The  family  Mustelidce  includes  several  of  our  most  valuable 
fur-bearing  animals,  many  of  which  are,  however,  now  nearly 
exterminated.  The  otter,  mink,  ferret,  weasel  and  martin  all 
have  long  slender  bodies  and  very  short  legs.  The  otter,  Lutra 
canadensis,  used  to  be  common  along  many  of  our  streams  but 
is  now  rarely  found  except  in  the  far  north.  The  fur  of  the  sea 
otter,  Latax  Ittlris,  is  now  most  valuable  and  rare.  Specimens 
are  still  taken  occasionally  along  the  Alaska  coast.  Minks, 
Lutreola  spp.,  are  still  rather  common,  occurring  along  the 
banks  of  many  of  our  streams.  There  are  several  species  of 
weasels,  the  most  common  one  of  which,  Putorius  erminea,  is 
often  called  the  ermine.  It  is  brown  in  summer  and  white  in 
winter.  Weasels  are  often  serious  pests  of  the  poultry  yards, 
for  they  usually  kill  many  more  chickens  or  ducks  or  geese 
than  they  can  eat.  They  do  some  good  on  the  farm  by  catch- 
ing rats  and  field  mice. 

The  wolverine,  or  skunk-bear,  Gulo  luscus,  looks  not  unlike  a 
large  skunk  or  a  badger  except  that  it  is  without  stripes. 
It  occurs  throughout  the  west  and  north,  and  is  often 
called  glutton,  on  account  of  its  habit  of  eating  almost  any- 
thing it  can  find  and  seemingly  maliciously  destroying  much 
else.  The  skunks,  Mephitis  spp.,  and  Spilogale  spp.,  are  well 


MAMMALS  315 

known  in  all  communities.  The  ill-smelling  fluid  which  causes 
other  animals,  including  man,  to  keep  a  respectful  distance  when 
possible,  is  secreted  by  two  glands  near  the  base  of  the  tail. 
The  skunks  are  very  destructive  in  poultry  yards,  but  since 
their  skins  are  now  much  used  as  substitutes  for  otter,  mink  and 
sable,  they  will  probably  soon  be  much  less  common  than  at 
present.  The  badgers,  Taxidea,  are  broad,  flat,  short-legged 
animals  living  in  burrows  throughout  the  west,  and  feeding  on 
ground-squirrels  and  any  other  small  animals  that  they  can 
capture. 

The  raccoons,  or  "  coons, "  family  Procyonida,  are  found  in 
wooded  regions  throughout  America.  They  usually  live  in 
hollow  trees,  and  eat  almost  all  kinds  of  food.  They  sometimes 
give  poultry  raisers  a  good  deal  of  trouble,  but  are  usually 
easily  trapped  or  hunted  and  killed. 

The  bears  belong  to  the  family  Ursula,  and  all,  except  the 
polar  bear,  to  the  genus  Ursus.  They  feed  on  almost  any  kind 
of  meat  or  fish  that  they  can  obtain,  and  on  roots,  berries, 
honey  a'nd  many  other  things.  Unless  fighting  in  defense  of 
self  or  young  they  will  seldom  molest  man,  but  some  of  the 
larger  species  make  occasional  destructive  raids  on  stock 
ranches  where  they  may  kill  sheep  or  hogs  or  young  cattle.  The 
polar  bear,  Thalarctos  maritimus,  is  found  throughout  the  Arctic 
regions  and  is  one  of  the  largest  of  our  bears.  The  fur  is  white 
all  the  year  around.  The  black  bears,  U.  americanus,  are  the 
most  common  and  widely  distributed.  They  vary  greatly  in 
color  and  size,  and  are  sometimes  called  brown  bears  or  cinna- 
mon bears.  The  huge  grizzly  bear,  U.  horribilis,  occurs 
throughout  the  mountain  regions  of  the  west  but  is  rapidly 
being  exterminated.  The  long  brown  hairs  that  make  up  the 
heavy  coat  are  tipped  with  gray,  hence  the  name  "  silver  tip " 
so  often  used.  Several  other  species  occur  in  America,  the 
largest  of  all  the  bears  being  the  great  brown  Kodiak  bear, 
U.  middendorffi,  of  Kodiak  Island,  Alaska. 

The  seals  and  the  sea-lions,  order  Pinnipedia,  are  all  aquatic, 
mostly  marine  animals.  The  true  seals,  family  Phocida,  have 
their  legs  so  thoroughly  modified  for  swimming  that  they  are  of 
little  use  on  land.  The  common  harbor  seals,  Phoca  mtulina, 


3i6    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

have  short  stiff  hair  and  are  of  no  value  for  fur.  The  harp  seal, 
or  Greenland  seal,  Phoca  groenlandica,  is  highly  prized,  the 
value  of  the  catch  sometimes  reaching  nearly  half  a  million  of 
dollars. 

The  fur  seals  and  the  sea-lions  belong  to  the  family  Otariidee. 
The  legs  of  these  animals,  while  well  adapted  for  swimming,  are 
still  of  some  use  on  land,  so  that  some  of  them  can  travel  quite 


FIG.  135. — A  fur  seal,  Callorhinus  alascanus,  male,  the  herd  on  the  beach 
in  the  background.     (Photograph  by  G.  A.  Clark.) 

rapidly,  though  awkwardly,  for  a  considerable  distance.  The 
fur  seals,  genus  Callorhinus,  are  by  far  the  most  important 
members  of  the  group.  The  value  of  the  catch  for  1910  was 
$437,000,  and  for  1911,  $423,000.  They  are  found  on  land  only 
on  certain  islands  in  the  Bering  Sea  where  they  come  for  breed- 
ing. Early  in  the  spring  the  old  males  arrive  on  the  rocky 
shores  of  the  islands  and  await  the  females,  which  begin  to  come 
early  in  June.  Each  male  gathers  around  him  a  group  of 


MAMMALS  317 

females,  sometimes  as  many  as  thirty  to  eighty  and,  fighting 
away  all  intruders,  keeps  guard  over  the  harem  for  the  rest  of 
the  season.  The  young  seals,  or  pups,  are  born  soon  after 
the  females  arrive  on  the  rookeries,  the  mothers  nursing  them 
until  they  are  themselves  able  to  go  into  the  water  for  their 
food. 

In  September  the  seals  of  the  Pribilof  Islands  begin  leaving 
and  in  about  two  months  they  are  all  gone.  They  go  as  far 
south  as  the  Santa  Barbara  Islands  off  the  California  coast, 
then  turning  north  again  they  keep  along  the  general  trend  of 
the  shores  in  water  about  one  hundred  fathoms  deep.  After 
traveling  some  6000  miles  or  more  without  touching  land,  they 
again  reach  their  breeding  grounds.  The  Russian  herd  of  the 
Commander  Islands  makes  a  similar  migration  along  the  coast 
of  Japan. 

When  Alaska  first  became  a  territory  of  the  United  States, 
there  were  probably  between  two  and  three  million  seals  on  the 
rookeries  of  the  Pribilof  Islands,  but  the  relentless  way  in  which 
they  have  been  hunted  in  the  open  sea  in  the  past  thirty, years, 
has  greatly  reduced  the  size  of  this  herd.  In  the  early  days  of 
Russian  control  the  seals  were  killed  indiscriminately.  In 
1834  the  Russians  established  regulations  protecting  females  on 
the  breeding  grounds  and  permitting  only  young  males,  or 
bachelors,  to  be  killed.  This  has  been  the  method  of  land 
sealing  ever  since.  In  1879  pelagic  sealing  began  and  many  of 
the  mother  seals  were  killed  while  they  were  on  their  migra- 
tion journey  or  their  feeding  excursions.  Thousands  of  the 
pups  were  left  on  the  beach  to  starve,  and  the  herds  were 
depleted.  In  1870  there  were  about  2,500,000  seals  in. the 
American  herd,  in  1890,  1,000,000  and  in  1912  only  about 
250,000.  The  Russian  herd  has  been  about  one-half  as 
large. 

In  1911  the  four  governments,  Russia,  the  United  States, 
England  and  Japan,  the  two  former  being  owners  of  the  herds 
and  the  two  latter  participating  in  pelagic  sealing,  entered  into 
a  treaty  suspending  pelagic  sealing  for  fifteen  years.  In  the 
law  of  1912  designed  to  give  effect  to  this  treaty,  our  Congress 
included  a  provision  prohibiting  the  land  killing  of  males  for 


3i8    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

five  years.     Thus  under  present  regulations  no  seals  may  be, 
killed  except  the  few  that  are  allowed  the  natives  for  food. 

The  California  sea-lion,  Zalophus  calif ornianus,  and  S teller's 
sea-lion,  Eumetopias  stelleri,  are  both  found  along  the  rocky 
shores  of  the  north  Pacific.  Their  hair  is  coarse*  and  of  little 
value  for  fur,  but  the  skins  are  used  for  many  purposes. 

The  Pacific  walrus,  Odobenus  obesus,  is  the  most  important 
species  of  the  walrus  family,  Odobenidce.  These  animals  attain 
a  length  of  ten  to  twelve  feet  and  a  weight  of  1500  to  2000 
pounds.  The  canine  teeth  are  developed  into  two  huge  valu- 
able ivory  tusks  sometimes  as  much  as  two  feet  long.  They 
feed  principally  on  shell  fish  and  crustaceans  which  they  dig  up 
from  the  bottom  of  the  shallow  bays.  These  huge  clumsy 
animals,  now  comparatively  few  in  numbers,  were  formerly 
abundant,  and  furnished  the  natives  of  the  northern  shores 
food,  fuel,  oils  and  excellent  skins  which  were  used  in  build- 
ing houses,  boats,  dog  harness,  etc. 

The  order  Primates  is  the  highest  order  of  animals,  and  in- 
cludes the  lemurs,  monkeys,  baboons,  apes  and  man.  The 
lemurs,  family  Lemuroidea,  are  the  lowest  members  of  the 
group.  These  are  strange,  squirrel-like  or  fox-like  little  ani- 
mals living  in  the  trees  and  bushes  in  Madagascar  and  other 
near-by  regions.  The  marmosets,  family  Callithricida,  are 
curious  small  long-haired,  long-tailed  animals,  but  little  higher 
in  the  scale  than  lemurs.  They  are  found  in  tropical  America. 
The  New  World  monkeys,  family  Cebida,  are  mostly  smaller 
and  weaker  than  the  Old  World  forms.  Nearly  all  have  long 
prehensile  tails  which  greatly  aid  them  in  their  travels  in  the 
tree  tops.  They  all  have  a  wide  nose  in  which  the  nostrils  are 
separated  by  a  broad  septum  and  the  openings  directed 
laterally.  On  this  account  they  are  known  as  platyrrhine 
monkeys,  while  the  Old  World  monkeys,  which  have  the  nose 
septum  narrow  and  the  openings  of  the  nostrils  directed  for- 
ward, are  called  catarrhine  monkeys. 

The  family  Cercopithecida  includes  monkeys  of  Japan, 
Asia,  Africa  and  the  Malay  Archipelago.  None  of  these  has 
a  prehensile  tail  and  some  have  only  a  very  short  tail.  The 
red-faced  monkey  of  Japan  is  one  of  the  best  known  of  these. 


MAMMALS 


The  baboons,  of  which  there  are  about  sixteen  species,  are 
among  the  largest  members  of  the  family.  They  are  bad 
tempered,  always  ready  for  a  fight,  and,  as  they  usually  travel 
in  small  companies,  they  make  very  formidable  foes. 


>' 


FIG.  136. — "Bob,"  a  monkey  of  the  genus  Cercopithecus.    (Photograph 
by  D.  S.  Jordan.) 

The  family  Simiida,  includes  the  anthropoid  apes,  namely,  the 
gibbon,  orang-utan,  chimpanzee  and  gorilla.  The  gibbons  are 
small,  long-armed  and  arboreal.  About  six  species  are  found 
in  the  Malay  Peninsula  and  adjacent  islands.  The  orang- 


320    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

utans  are  found  in  the  same  regions  as  the  gibbons.  They  are 
much  larger,  reaching  a  height  of  four  feet  or  more.  They  too 
live  among  the  tree-tops  and  swing  themselves  from  limb  to 
limb  by  their  long  powerful  arms. 

In  many  respects,  such  as  the  shape  of  the  head  and  the 
hands  and  the  size  and  activity  of  the  brain,  the  chimpanzee, 
Pan  troglodytes,  is  much  more  man-like  than  any  of  the  other 
apes.  It  is  a  very  imitative  and  teachable  animal  and  captive 
individuals  are  often  trained  to  do  many  things  that  men  do. 
The  chimpanzees  live  in  tropical  Africa.  The  gorilla,  Gorilla 
gorilla,  is  the  largest  of  the  apes  and  structurally  most  like 
man.  Its  shorter  arms  and  its  habit  of  walking  erect  on  the 
ground  indicate  a  higher  stage  of  development,  but  the  skull 
is  much  less  man-like  than  is  the  skull  of  the  chimpanzee. 

Belonging  to  the  same  order,  similar  in  structure,  yet  sepa- 
rated by  the  widest  gulf  as  regards  development  of  the  intel- 
lect, the  power  of  speech,  and  many  other  qualities,  is  the 
human  species,  Homo  sapiens,  the  only  species  in  the  family 
Hominidce.  Although  the  members  of  the  lowest  savage  tribes 
differ  in  appearance  from  the  highest  civilized  Americans  or 
Europeans  more  than  do  the  members  of  different  families  in 
some  groups  of  the  lower  animals,  yet  all  human  beings  are 
considered  as  belonging  to  the  same  species  for  there  are  no 
constant  structural  differences.  We  may,  however,  recognize 
several  more  or  less  distinct  races  or  varieties.  There  have 
bedn  discovered  in  Europe  the  fossilized  remains  of  at  least 
one  and  perhaps  two  extinct  species  of  man.  These  species 
were  much  more  primitive  and  bestial  in  structure  than  man 
of  to-day,  but  they  are  unmistakably  the  progenitors  of  the 
present-day  human  type.  They  carry  the  history  of  man 
back  to  the  beginning  of  the  present  or  Pleistocene  geological 
epoch.  This  was  certainly  at  least  five  hundred  thousand 
years  ago. 


CHAPTER  XXVI 
DOMESTICATED  ANIMALS1 

The  animals  that  we  call  domestic,  while  sometimes  of  kinds 
and  appearance  very  different  from  any  wild  animals  that  we 
know,  are  yet  certainly  all  descended  from  kinds  that  are  or 
were  originally  wild.  There  are  wild  pigs,  wild  goats,  wild 
doves,  wild  ducks,  wild  silk-worms.  There  are  no  wild  dogs 
nor  probably  any  longer  any  true  wild  horses,  but  it  is  easy  for 
us  to  see  from  what  wild  animals  our  tame  dogs  and  horses  have 
been  derived. 

It  is  certain  from  the  records  of  history,  and  from  ancient 
pictures  and  carvings,  and  still  more  ancient  bones  and  relics, 
that  man  has  had  domesticated  animals  for  the  last  ten  thou- 
sand years.  How  long  before  that  he  made  a  practice  of  tam- 
ing and  using  and  perhaps  breeding  his  animal  companions  of 
pre-historic  times  we  may  never  know.  In  the  caves  where 
are  found  the  bones  and  rude  implements  of  early  man,  that 
primitive  man  of  the  Glacial  epoch,  there  are  also  found  the 
bones  of  various  animals,  but  these  seem  to  be  the  remains  of 
kinds  that  were  either  his  victims  or  his  conquerors  in  the  raw 
struggle  for  existence  of  those  ancient  times.  However,  when 
the  pre-historic  Egyptians  and  Cretans  emerged  from  the 
Stone  Age  into  the  earliest  light  of  history  they  appear  with 
cattle,  sheep,  donkeys  and  dogs  already  fully  domesticated. 

Artificial  Selection. — The  domestication  of  animals  is  the 
result  of  several  different  factors.  First,  there  may  be  the 
simple  capture  and  taming  and  using  of  individuals  of  a  wild 
species.  Then  comes  the  rearing  in  captivity  of  young  of  this 
species,  and  the  easier  taming  of  these  home-reared  individuals 
because  of  their  earlier  acquaintanceship  with  man. 

1  Most  of  this  chapter  is  taken  from  Chapter  XIX  of  "The  Animals 
and  Man,"  by  the  senior  author. 

21  321 


322    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

But  in  this  rearing  in  captivity  a  new  element  enters  almost 
at  once.  That  is  the  choosing  or  selection  of  certain  of  these 
young  to  be  allowed  to  grow  up,  and  again  the  choosing  among 
these  when  grown  up  of  those  to  be  the  parents  of  more  young. 
This  selection  may  be  almost  unconsciously  done,  or  it  may  be 
made  intentionally  and  carefully,  so  as  to  preserve  the  most 
desirable  individuals  and  have  them  give  birth  to  others  like 
themselves. 

Then  there  comes  the  crossing  of  special  individuals  or  the 
hybridizing  with  other  races  in  the  hope  of  adding  or  combin- 
ing in  the  offspring  the  desirable  qualities  of  both  kinds  of 
parents.  It  is  this  careful  selecting  and  crossing  that  are 
usually  meant  when  animal  breeding  is  spoken  of.  And  our 
modern  hosts  of  kinds  or  races  of  domesticated  animals,  the 
scores  of  sorts  of  dogs  and  cats  and  cattle  and  pigeons  and 
ducks,  have  all  been  produced  by  "breeding."  The  acts  of 
choosing  and  hybridizing  and  choosing  again  and  rearing  from 
these  chosen  offspring  and  again  from  each  following  genera- 
tion until  a  form  is  arrived  at  very  different  in  appearance  or 
habit  from  the  original  ancestor  are  called  also  artificial  selec- 
tion. It  was  largely  on  a  basis  of  his  observations  of  the 
methods  and  results  of  artificial  selection  that  Charles  Darwin 
founded  his  great  theory  of  natural  selection,  which  is,  simply, 
that  nature  unconsciously  chooses  or  selects  among  animal  or 
plant  individuals  and  kinds  through  the  survival  and  producing 
of  young  by  those  types  born  with  traits  advantageous  in  the 
struggle  for  existence,  this  struggle  being  inevitable  on  account 
of  the  geometrical  ratio  by  which  animals  multiply. 

The  art  of  the  animal  breeder  has  reached  in  these  later  days, 
the  days  since  Darwin  particularly,  a  very  high  stage  of  devel- 
opment. It  is  becoming  a  science,  because  the  breeders  are 
studying  the  laws  of  variation  and  heredity  and  making  their 
hybridizations  and  selections  on  a  basis  of  the  scientific  knowl- 
edge of  these  laws  (see  next  chapter). 

An  important  thing  to  note  in  connection  with  animal 
breeding  and  artificial  selection  is  that  the  selecting  and  modi- 
fying are  all  made  to  change  the  animals  along  lines  wholly 
determined  by  man;  lines  that  make  the  animals  more  useful 


DOMESTICATED  ANIMALS 


323 


or  pleasing  or  curious  to  us  but  not  better  fitted  to  survive  in 
nature.  In  fact,  most  of  these  artificially  induced  changes  tend 
to  unfit  the  animal  for  success  in  life  unaided  by  man;  they  are 
mostly  degenerative  changes.  The  loss  of  flight,  the  shortening 
of  legs,  the  over-development  of  fat,  the  production  of  crests 
and  plumes  and  ruffs,  the  loss  of  horns,  the  sluggishness  and 
helplessness  that  characterize  the  domestic  animals  of  different 


FIG.  137. — Assyrian   hunters   with  great  dogs;  from  an  Assyrian   wall 
relief  of  668  B.C.,   now  in  the  British  Museum.     (After  Keller.) 

kinds,  are  all  characters  and  conditions  of  degeneration.  As 
an  outcome  of  the  modern  great  interest  and  activity  in  the 
methods  and  results  of  producing  new  races  and  types  of 
domesticated  animals,  the  history  of  the  origin  of  many  of  the 
more  widespread  and  useful  of  these  animal  races  has  been 
unravelled.  The  following  paragraphs  give  in  briefest  possible 
form  some  interesting  facts  about  the  origin  of  our  more 
familiar  animal  companions. 


324    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

There  seems  to  be  no  doubt  that  the  dog  is  the  oldest 
domesticated  animal,  as  he  is  also  the  closest  and  the  most 
nearly  universal  animal  companion  of  man.  From  among  the 
crudest  of  living  human  races  to  the  most  civilized  and  culti- 
vated, the  dog  is  everywhere  and  always  at  man's  side,  serving 
him  as  faithful  helper  in  the  chase,  in  caring  for  his  flocks  and 
home,  and  as  companion  of  his  table  and  fireside.  The  Bush- 
men of  Australia,  the  Esquimaux  of  the  Arctic,  the  Indians  of 
the  prairie  and  pampas,  the  cannibals  of  the  scattered  Paci- 
fic Islands  as  well  as  the  Caucasians  of  the  world's  great  capi- 


FIG.  138. — Thibet  wolf,  Canis  niger,  one  of  the  wild  ancestors  of  dogs. 
(After  Sclater.) 


tals  have  their  dog  companions.  And  as  is  inevitable  under 
such  many  and  different  human  conditions  and  stages  of 
civilization  the  kinds  of  dogs  are  many  and  very  different. 
About  fifty  breeds  of  sporting  dogs  and  fifty  of  non-sporting 
dogs  are  recognized  by  fanciers.  There  are  many  books  filled 
with  the  descriptions  and  illustrations  of  these  varieties,  which 
range  in  size  from  the  tiny  toy  dogs  of  Paris,  that  a  lady  can 
carry  in  her  muff,  to  the  great  Danes  and  St.  Bernards  that 
stand  three  feet  high  and  weigh  one  hundred  and  fifty  pounds. 
The  origin  of  all  these  dog  races  is  not  to  be  found  in  any  one 


DOMESTICATED  ANIMALS  325 

wild  species  of  dog-like  animal,  but  in  several.  These  wild 
ancestors  of  the  dog  are  certain  wolves  and  jackals  of  various 
lands.  Dogs  are  probably  descended  from  at  least  seven  such 
wild  species,  namely,  the  jackal,  Canis  aureus,  of  western  Asia, 
the  landga,  Canis  pallipes,  of  India,  the  jackal  wolf,  Canis 
anthus,  of  northeast  Africa,  the  walgie,  Canis  niger,  of  Thibet, 
and  the  coyote,  Canis  latrans,  and  dun-gray  wolf,  Canis  occi- 
dentalis,  of  North  America. 

The  house  cats,  on  the  contrary,  as  various  and  as  widely 
distributed  as  they  are,  seem  to  be  all  descended  from  a  single 
wild  species.  This  is  the  dun  wild-cat,  Felis  maniculata,  of 
northeast  Africa.  All  of  the  present  races  of  house  cats  trace 
their  lineage  back  to  Egypt.  That  the  Egyptians  were  much 
given  to  the  possession  and  care  of  cats  the  numerous  cat 
mummies  of  their  graves  show.  Cats  were  a  sacred  animal 
for  them  under  the  special  protection  of  the  goddess  Bast,  a 
goddess  introduced  into  Egypt  by  Semitic  influence.  The 
fanciers  now  recognize  about  thirty  established  races  of  cats. 
They  are  grouped  in  two  main  classes,  namely,  long-haired 
cats  and  short-haired  cats,  and  in  both  groups  appear  certain 
repeated  colors  as  white,  cream,  gray,  silver,  yellow,  black, 
smoke  "blue,"  brown,  orange,  "red,"  etc.  The  pattern  may 
be  solid  color  or  banded  (tabby)  or  spotted  (tortoise-shell)  in 
different  colors.  There  is  a  Mexican  hairless  cat  (just  as  there 
is  a  Mexican  hairless  dog).  The  so-called  Manx  cats  are 
always  tailless,  but  very  short-tailed  or  even  tailless  individuals 
occur  occasionally  in  several  other  races,  at  least  among  the 
short-haired  kinds. 

The  horses  of  modern  times  can  be  traced  back  to  two  wild 
ancestors,  namely,  Equus  przewalski,  of  northern  Asia,  from 
which  all  the  Oriental,  Mongolian,  Arabian,  North  African 
and  East  European  races  have  sprung;  and  Equus  caballus 
fossilis,  or  the  diluvial  horse,  of  Europe,  from  which  the  Ger- 
man, Norman,  English  and  West  European  horses  generally 
have  risen.  In  America  fossil  horses  have  been  found  back 
through  a  series  of  geologic  ages  as  far  as  the  beginning  of  the 
Tertiary  Age  forming  a  connected  series  from  the  small 
Eohippus  of  the  lower  Eocene  period,  about  the  size  of  a  fox, 


326  ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  with  four  toes  and  splint  of  the  fifth  digit  on  each  hind 
foot;  through  Protorohippus  and  Orohippus  of  the  Middle 
Eocene,  about  fourteen  inches  high,  with  four  toes  on  front 
feet  and  three  toes  on  hind  feet,  and  no  splints;  through  Meso- 
hippus  of  the  Oligocene,  about  the  size  of  a  coyote,  and  with 
three  toes  on  all  its  feet;  through  Protohippus  and  certain  other 
kinds  of  the  Middle  Miocene,  about  as  large  as  Shetland  ponies 
and  with  three  toes  on  all  feet  but  with  the  side  toes  not  touch- 
ing the  ground;  to  Equus,  which  first  appeared  in  the  Pleisto- 


FIG.  139. — Restoration  of  the  four-toed  horse;  based  on  a  mounted 
skeleton,  sixteen  inches  high,  in  the  American  Museum  of  Natural  History. 
(After  C.  R.  Knight.) 

cene  with  only  one  developed  toe  and  splints  of  the  second  and 
fourth  on  each  foot. 

The  color  of  the  prehistoric  horse  is  not  known,  but  it  was 
probably  dun  with  more  or  less  well-defined  stripes  like  a 
zebra.  The  bones  of  human  beings  have  been  found  associ- 
ated with  those  of  prehistoric  horses  in  South  America  and  in 
Europe.  Remains  of  horses  are  associated  in  Europe  with 
human  relics  of  the  Bronze  Age,  and  figures  of  the  wild  horse 


DOMESTICATED  ANIMALS 


327 


are  abundant  among  the  drawings  made  by  late  Glacial  man  on 
cave  walls  in  Spain  and  France. 

About  a  dozen  living  natural  species  and  sub-species  of  the 
genus  Equus  are  known,  including  horses,  asses,  zebras,  and  the 
now  nearly  if  not  quite  extinct  quagga.  Of  domesticated 
races  of  horses  and  asses  the  number  must  run  to  more  than  a 
score  of  well-marked  distinct  breeds,  varying  in  size  from  the 


FIG.  140. — Arion,    a    record-holding    American    trotting    horse.     (After 

Plumb.) 

minute  ponies  of  the  north  British  islands  to  the  great  Clydes- 
dale and  Percheron  draught  animals. 

Donkeys  have  been  derived  from  two  wild  species,  the  Nu- 
bian Desert  donkey,  Equus  toeniopus,  and  the  onager,  Equus 
onager,  of  eastern  Asia.  Tame  donkeys  are  figured  in  the 
earliest  of  Egyptian  and  Assyrian  drawings  and  carvings. 

The  races  of  domesticated  hogs  are  also  descended  from  two 
wild  races,  the  European  wild  boar,  Sus  scrofa,  and  another 


328    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


FIG.  141. — The  Banteng,  Bos  sondaicus,  or  wild  ox  of  Java  and  South 
Asia.     (After  Keller.) 


FIG.  142. — White  Hall  Sultan,  a  Shorthorn  prize  bull.     (After  Plumb.) 


DOMESTICATED  ANIMALS 


329 


species,  Sus  vittatus,  from  eastern  Asia.  From  this  latter  the 
swine  of  China  and  those  of  the  Romans  and  indeed  most  of  the 
European  races  have  descended.  The  lake  dwellers  of  Switzer- 
land had  domesticated  hogs,  and  pig  remains  have  been  found 
with  prehistoric  relics  in  Denmark.  China  has  had  domesti- 
cated swine  for  thousands  of  years. 

The  many  races  of  cattle  all  seem  to  trace  back  to  two 
sources,  the  wild  banteng,  Bos  sondaicus,  of  Java  and  South 


^- 

FIG.  143. — The  wild  sheep  of  the  Trans-Caspian  steppes,  Ovis  arkal. 
(After  Keller.) 

Asia,  from  which  are  derived  the  zebus,  the  old  Egyptian  long- 
horns,  and  many  of  the  races  of  Europe,  such  as  the  Spanish, 
Albanian,  Sardinian,  Polish  and  brown  Alpine  cattle;  and  the 
primitive  wild  ox  of  Europe,  Bos  primigenius,  from  which  have 
descended  most  of  the  English,  North  German,  and  Holland 
races.  This  wild  species  persisted  in  Germany  until  the  twelfth 
century  and  in  Poland  up  to  the  eighteenth  century.  A 
few  persons  in  America  have  tried  to  create  a  hybrid  race  by 


330    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

crossing  domestic  cattle  with  the  buffalo,  but  probably  no 
permanent  result  has  been  reached. 

The  domesticated  races  of  sheep  seem  to  have  had  three 
original  wild  sources,  Ovis  musimon  of  South  Europe,  Ovis 
arkal  of  Western  Asia,  and  Ovis  tragelaphus  of  North  Africa. 
Most  of  our  present  European  and  American  races  come  from 
the  second  named  of  these  wild  kinds.  The  earliest  certain 
remains  of  tame  sheep  appear  in  the  Stone  Age.  In  the  Bronze 


FIG.  144. — Typical  American  Merino  ewe,  a  highly  specialized  breed  of 
sheep,   with  fine,  close-set  wool.     (After  Shaw.) 

Age  sheep  domestication  was  well  developed.  The  oldest 
Assyrian  drawings  picture  domesticated  sheep,  among  which 
the  still  persisting  fat-tailed  race  appears.  The  Egyptians  had 
domesticated  sheep  in  the  times  before  the  Pharaohs. 

Our  goats  also  are  descended  from  three  wild  races,  namely, 
Capra  cegagrus  of  Western  Asia,  Capra  falconeri  and  Capta 
jemlaica  of  the  Himalayas.  The  earliest  prehistoric  indications 
of  tame  goats  come  from  the  times  of  the  Lake-dwellers.  Jn 
the  Bronze  Age  they  were  common. 


DOMESTICATED  ANIMALS  331 

Other  mammals  that  are  represented  by  domestic  races  are 
the  camel,  the  elephant,  the  water  buffalo,  the  rabbit,  the 
ferret,  the  reindeer,  the  lama  and  alpaca,  the  guinea-pig,  the 
mouse,  the  rat,  etc.  But,  excepting  the  rabbit,  the  domes- 
ticated forms  of  these  animals  are  only  wild  species  tamed 
and  reared  under  man's  hand  but  not  much  modified  by  breed- 
ing. There  are  about  fifteen  races  of  domesticated  rabbits 
all  of  which  probably  trace  their  lineage  back  to  wild  species 
native  to  Spain  and  Southern  France. 


FIG.  145. — Silver-laced  Wyandotte  cockerel. 

Of  birds  there  are  domesticated  races  of  doves,  chickens, 
turkeys,  ducks,  geese,  swans,  pea-fowls,  pheasants,  canary 
birds,  ostriches,  cormorants  and  others.  Of  these  the  doves 
and  chickens  are  represented  by  the  most  varieties.  Brown, 
an  English  authority  on  domestic  birds,  lists  more  than  seventy 
races  of  chickens  now  living,  thirteen  races  of  ducks,  ten  of 
geese,  and  eight  of  turkeys.  Of  pigeons  there  must  be  nearly  as 
many  domestic  races  as  there  are  of  chickens.  And  yet  all  of 


332    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

them,  with  all  their  extraordinary  variety  of  crests,  and  ruffs, 
and  tails  and  plumage  pattern,  and  all  their  various  special 
manners  such  as  tumbling,  dancing,  and  the  like,  are  descended 
from  a  single  wild  species,  the  common  rock  dove,  Columba 
lima,  of  Europe,  Asia  and  North  Africa. 

The  domestic  races  of  chickens  are  by  some  naturalists  also 
held  to  be  descended  from  a  single  wild  species,  the  jungle  fowrl, 
Callus  bankiva,  which  ranges  from  Hindukoosh  to  the  Chinese 
island  of  Hainau  and  through  most  of  the  Indonesian  islands. 
But  other  naturalists  believe  that  one  or  two  other  wild  species 
of  fowl  are  concerned  in  the  ancestry  of  our  barnyard  hen. 


\ 


FIG.  146. — Wild  jungle  fowls,  Callus  bankiva,  of  India.     (After  Brown.) 

The  domestic  ducks  are  derived  from  the  wild  duck,  Anas 
boschas,  and  have  evidently  originated  from  this  ancestor  inde- 
pendently both  in  China  and  in  Europe.  The  domestic  geese 
seem  to  have  an  older  origin  than  the  ducks;  in  fact,  geese  are 
probably  the  oldest  of  domesticated  birds.  The  ancestor  of 
our  races  is  the  wild  species,  Anas  cinereus.  The  Chinese  races, 
however,  are  descended  from  Anas  cygmoides,  and  the  early 
Egyptians  seem  to  have  tamed  and  used  the  Nile  goose, 
Chenalopex  egyptiaca. 

The  domesticated  peacocks  are  descended  from  a  wild  species 


DOMESTICATED  ANIMALS  333 

of  India,  Pavo  cristatus.  The  turkeys  trace  their  ancestry  to 
the  wild  Meleagris  gallopavo  of  North  America.  The  swans  are 
really  only  tamed  wild  kinds.  Common  species  are  the  white 
swan  of  Europe,  Cygnus  olor,  the  black  swan  of  New  Holland, 
Cygnus  atratus,  and  the  black-necked  swan  of  South  America, 
Cygnus  nigricollis.  The  pheasants  also  are  so  far  practically 
only  partially  tamed  wild  species,  whose  eggs  are  usually 
hatched  under  turkeys.  Most  of  the  kinds  kept  are  from 
the  Orient. 

Canary  birds  are  descended  from  the  wild  species,  Fringilla 
canariensis,  of  the  Canary  Islands.  But  there  has  been  some 
crossing  of  them  with  other  species  of  wild  birds,  especially 
certain  sparrow  and  finch  kinds.  There  are  now  numerous 
domesticated  races  which  vary  structurally  and  in  color-pattern 
as  well  as  in  voice.  Many  of  the  characters  resemble  the  ruffs, 
crests,  and  other  plumage  eccentricities  of  pigeons.  The  prin- 
cipal place  of  canary  bird  breeding  at  present  is  in  the  Harz 
Mountains  of  Germany. 

Tamed  cormorants  are  used  by  the  Chinese  and  Japanese  as 
fishing  birds,  somewhat  as  falcons  were  used  in  days  of  old  as 
hunting  birds.  Indeed,  in  these  same  days  cormorants  were 
used  for  sport.  Charles  I  of  England  had  a  "master  of  the 
cormorants."  Nowadays,  however,  cormorant  fishing  is 
a  practical  means  of  gaining  food.  A  ring  is  placed  about 
the  neck  of  each  bird  so  as  to  prevent  it  from  swallowing  the 
fish  it  catches.  Several  different  species  of  cormorants  are 
thus  used. 

The  ostrich  is  the  most  recent  addition  to  the  ranks  of  domes- 
ticated birds.  The  tamed  species  is  derived  directly  from  the 
widely  distributed  African  ostrich,  Struthio  camelus. 

Besides  mammals  and  birds  two  or  three  species  of  fish,  such 
as  the  carp  and  goldfish,  may  be  caljed  domesticated.  This 
is  certainly  true  of  the  goldfish,  which  is  a  product  of  Chinese 
animal  breeding.  S  ome  most  bizarre  forms  have  been  produced 
in  the  thousand  or  more  years  in  which  this  fish  has  been  a 
subject  of  selection  and  hybridization. 

There  are  also,  finally,  at  least  two  species  of  insects  that  have 
a  right  to  be  called  domesticated  animals,  namely,  the  honey- 


334    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

bee  and  the  mulberry  silk- worm.  The  honey-bee,  Apis  mellifica, 
has  "been  long  used  by  man  to  obtain  honey  from,  but  only  in 
modern  times  has  the  species  been  the  subject  of  true  "breed- 
ing." However,  already  several  distinct  races  have  been 
produced.  The  bee  is  native  to  Europe  and  Asia,  and  "wild" 
honey-bees  in  America  are  only  communities  established  by 
wandering  swarms  from  hives,  or  from  other  "  wild "  commu- 
nities which  have  descended  from  such  escaped  swarms  (see 
p.  185). 

The  silk-worm,  Bombyx  mori,  has  on  the  contrary  been  an 
artificially  bred  animal  for  five  thousand  years,  and  scores  of 
races,  with  differently  colored  and  shaped  cocoons,  exist.  The 
actual  wild  species  from  which  the  domesticated  races  are 
descended  is  not  known,  but  it  is  most  likely  some  one  of  the 
several  wild  species  of  northern  India.  The  cocoons  of  cer- 
tain of  these  wild  Indian  species  are  to-day  still  collected  for  the 
silk  and  sold  under  the  commercial  name  of  "Tussoor"  silk. 
The  ancient  breeding  and  care  of  silk-worms  was  mostly  done 
in  China  and  Japan.  To-day  it  is  carried  on  even  more  ex- 
tensively in  France  and  Italy  (see  p.  176). 


CHAPTER  XXVII 
ANIMAL  LIFE  AND  EVOLUTION 

In  all  this  book  so  far,  we  have  made  but  little  reference  to 
that  phase  of  the  study  of  animals  which  is  usually  called 
animal  evolution,  or  animal  bionomics.  We  have  taken  the 
many  species  of  animals,  and  the  great  variety  of  form  and 
manner  of  life  of  these  species,  as  facts,  not  problems;  and  we 
have  even  described  many  kinds  of  extraordinary  adaptations, 
or  modifications  of  structure  and  life  to  fit  their  possessors  to 
special  or  unusual  conditions,  without  suggesting  that  the  ques- 
tion of  the  origin  of  these  adaptations  presents  perhaps  the 
most  important  and  attractive  problem  in  all  the  study  of 
animals.  We  have  postponed  all  such  references  deliberately 
in  order,  primarily,  to  accent  the  facts  and  problems  of  eco- 
nomic zoology  throughout  the  book,  and,  secondarily,  so  that  we 
might  take  up  the  evolutionary  phase  of  animal  life  in  a  single 
compact  chapter  which  should  present  an  outline  of  the  present- 
day  status  of  knowledge  and  speculation  on  the  subject.  By 
putting  this  chapter  of  the  book  last  in  the  present  part  we  hope 
to  leave  as  a  final  impression  in  the  elementary  zoologist's 
mind  a  special  stimulus  to  further  interest  in  and  study  of 
animal  life.  For  it  is  exactly  the  evolutionary  phase  of  animal 
study,  the  pursuit,  that  is,  of  the  solution  of  questions  as  to  the 
why  and  how  and  the  origin  and  change  in  animal  form  and 
function  and  in  animal  kinds,  which  is  the  chief  inspiration  for 
the  really  philosophic  study  of  animal  life.  The  usefulness  of 
knowing  animals  and  their  life,  the  enjoyment  from  a  trained 
observation  of  their  manifold  forms  and  behavior,  and  the  drill 
obtained  from  a  careful  study  of  their  anatomy  and  physiology, 
are  all  really  achieved  by  human  endeavor  of  a  different  type 
from  that  required  for  the  solution  of  evolutionary  problems. 
And  all  of  them  are  much  more  really  within  the  possible  grasp 

335 


336    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

of  beginning  students.  So  that  we  believe  it  well  to  postpone, 
as  we  have  done  in  this  book,  any  special  consideration  of  the 
subjects  associated  with  animal  evolution  until  the  student  has 
had  some  personally  acquired  experience  in  the  study  of  the 
other  phases  of  zoology. 

Evolution  a  Fact. — Although  there  is  much  discussion  of  the 
causes  of  evolution  there  is  practically  none  any  longer  of 
evolution  itself.  Organic  evolution  is  a  fact,  demonstrated 
and  accepted.  The  many  important  open  questions  about 
evolution  concern  the  factors  that  originate  and  guide  it. 
Evolution  means  the  blood  relationship  of  organisms,  their 
descent  from  common  ancestors,  the  origin  of  kinds  by  the 
transformation  or  modification  of  other  already  existing  kinds. 

Evolution  was  not  discovered  by  Charles  Darwin  nor  by 
Lamarck,  whose  names  are,  however,  the  greatest  of  all  those 
associated  with  it.  It  grew  as  a  conception  and  a  belief  slowly 
through  all  the  years  from  the  times  of  the  Greeks  until  it 
received  its  two  most  positive  announcements  and  its  two  most 
plausible  explanations  from  Lamarck  and  Darwin.  Darwin, 
especially,  presented  such  a  full  and  convincing  statement  of 
the  facts  that  prove  the  reality  of  evolution  that  he  put 
evolution  for  all  future  time  into  our  accepted  understanding 
of  nature.  Hence  to  Darwin  belongs  the  greatest  merit  that 
attaches  to  any  name  connected  with  the  history  of  evolution. 

The  Causes,  or  Factors,  of  Evolution. — Evolution  has  two 
conspicuous  conditions  of  animal  (and  plant)  life  to  explain; 
first,  all  the  different  kinds  of  animals,  and,  second,  all  the 
various  adaptations  or  special  fittings  of  these  kinds  to  their 
environment,  so  that  they  may  live  successfully  as  individuals 
and  persist  as  species.  The  factors  or  causal  agencies  pro- 
posed to  explain  evolution  must,  therefore,  to  be  acceptable, 
explain  not  only  the  origin  of  species  but  their  adaptations. 
The  factors  proposed  are  many.  Most  conspicuous  among 
them  are  those  called  variation,  heredity,  'selection  and 
segregation. 

Variation  and  Mutation. — No  two  animals  in  the  world  are 
alike.  Whether  widely  related  or  so-called  "  identical  twins," 
products  of  a  single  egg,  there  are  differences  or  variations  be- 


ANIMAL  LIFE  AND  EVOLUTION  337 

tween  them.  Among  the  thousands  of  worker  bees  in  the 
same  hive,  all  produced  from  eggs  of  the  same  queen,  all  reared 
under  the  same  conditions,  and  all  looking  superficially  very 
much  alike,  the  trained  eye  of  the  student  of  variations  has  no 
difficulty  in  discovering  differences  in  size,  color,  character  of 
wing  venation,  number  of  wing  hooks,  etc.,  etc.,  differences 
indeed  in  the  condition  of  any  part  or  attribute  carefully 
studied.  The  variations  among  the  children  in  one  family, 
among  the  puppies  or  kittens  in  one  litter,  or  among  human 
individuals  or  dogs  or  cats  in  general,  are  readily  apparent, 
because  we  are  familiar  with  the  human  and  dog  and  cat 
bodies  and  attributes  and  readily  recognize  differences  among 
them.  But  these  differences  are  no  less  real  and  discoverable 
among  the  individuals  of  any  other  animal  species. 

These  variations  have  been  determined  to  be  of  two  kinds. 
One  kind,  called  acquired,  or  fluctuating,  is  produced  chiefly 
by  the  inevitable  environmental  differences,  kind  and  amount 
of  food,  etc.,  to  which  the  different  individuals  of  a  species  or 
even  of  one  brood  of  the  species,  are  subjected  during  their 
development  from  embryo  to  adult.  These  fluctuating  varia- 
tions are  apparently  not  directly  inherited,  and  hence  probably 
have  little  to  do  with  determining  evolutionary  change.  They 
may  have  some  importance  in  aiding  or  hindering  the  individual 
possessing  them  in  their  "  struggle  for  existence,"  and  by  help- 
ing to  save  or  lose  the  lives  of  these  individuals  determine  who 
among  them  shall  live  to  produce  offspring  and  who  shall  not. 
But  even  those  saved  by  the  possession  of  a  favorable  fluctu- 
ating variation  will  not  necessarily  hand  it  on  to  their  offspring, 
and  thus  impress  it  on  a  future  race. 

Variations  of  the  second  kind  are  called  congenital,  by  which 
is  meant  that  they  depend  primarily  upon  the  character  of 
the  germ  cells  from  which  the  new  individuals  are  produced, 
and  tend  to  appear  whatever  may  be  the  character  of  the 
environment  during  development.  These  variations  are 
directly  heritable,  that  is,  they  are  handed  on  to  the  offspring 
of  the  individuals  possessing  them.  What  causes  them  in  the 
first  place,  what  determines  that  the  fertilized  egg  cells  produced 
by  different  individuals  of  the  same  species  shall  differ  among 


338    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

themselves,  is  not  at  all  understood  as  yet.  These  congenital, 
heritable  variations  may  be,  and  usually  are,  small,  but  they 
may  also  be  large,  and  are  then  called  "sports."  They  have 
become  especially  familiar  in  recent  years,  under  the  name  of 
"mutations,"  in  the  condition  of  combinations  or  groups 
occurring  together,  and  thus  making  the  individuals  possess- 
ing them  readily  distinguishable  from  the  parent  type.  Recent 
important  discoveries  in  heredity  have  added  to  the  interest 
and  importance  of  these  congenital  variations,  and  have  thrown 
a  first  faint  light  upon  some  of  the  conditions  that  attend  their 
origin.  It  is  undoubtedly  true  that  they  are  really  the  most 
important  actual  beginnings  of  divergence  among  animals. 
They  are  the  building  stones  from  which  new  species  and  better 
adaptations  are  made.  The  importance  of  a  knowledge  of 
variations  on  the  part  of  animal  and  plant  breeders  is  obvious. 
It  is  especially  important  to  distinguish  between  the  heritable, 
or  congenital,  and  the  non-heritable,  or  acquired,  variations. 
Only  the  first  kind  can  be  taken  advantage  of  in  the  work  of 
making  new  races. 

Heredity. — The  extent  and  manner  in  which  we  inherit  our 
traits,  both  physical  and  mental,  from  our  parents  and  an- 
cestors has  always  been  the  subject  of  much  speculation  and 
study.  One  of  the  greatest  among  students  of  heredity  was 
Francis  Galton,  only  recently  dead,  whose  studies,  based 
largely  on  human  pedigrees,  resulted  in  the  formulation  about 
half  a  century  ago  of  what  is  known  as  Galton' s  "law  of 
ancestral  inheritance."  This  states  that  on  the  average  we 
receive  one-half  our  inheritance  from  our  parents,  one-fourth 
from  our  grandparents,  one-eighth  from  our  great  grand- 
parents, one-sixteenth  from  our  great,  great  grandparents,  and 
so  on  backward  by  halving  fractions,  the  sum  of  them  all  being 
one,  or  the  total  of  our  inherited  qualities. 

Such  a  law,  or  generalization,-  about  heredity  is  of  interest 
and  value,  but  it  gives  us  little  basis  on  which  to  predict  the 
specific  character  of  the  results  of  any  mating.  It  applies 
to  beings  and  characteristics  in  masses,  and  to  average  in- 
dividuals. And  it  does  not  say  what  half,  or  fourth,  or  eighth, 
we  shall  get  from  any  particular  pair  of  ancestors.  That  is, 


ANIMAL  LIFE  AND  EVOLUTION  339 

it  does  not  say  what  characteristics,  but  only  what  proportion 
of  a  whole  personality,  shall  be  inherited.  Hence  it  is  a  gen- 
eralization that  has  not  been  of  much  practical  use  to  breeders. 
Recently,  however,  great  progress  has  been  made  in  the  study 
and  elucidation  of  the  exact  heredity  behavior,  in  successive 
generations,  of  specific  traits  in  animals  and  plants,  so  that  there 
are  now  well  established  certain  new  generalizations,  or  "laws," 
of  heredity  that  are  of  immediate  practical  use  to  the  breeder. 
These  new  generalizations  are  known  as  the  Mendelian 
principles  of  heredity  because  some  of  them  were  first  dis- 
covered, by  experimental  work  with  plants,  by  Gregor  Mendel, 
an  Augustinian  monk  of  Austria.  He  did  his  work  and 
published  his  results  in  the  years  near  1860,  but  his  conclu- 
sions remained  practically  unknown  until  1900.  The  Mendel- 
ian principles  cannot  be  expressed  by  any  such  single,  simple 
and  comprehensive  generalization  as  the  Galtonian  law  of 
ancestral  inheritance.  They  do  not  attempt  to  treat  of 
the  inherited  personality  of  the  individual  as  a  whole  but 
concern  themselves  with  the  various  separate  characteristics 
or  traits  of  the  individual.  In  heredity  that  follows  the 
Mendelian  order — and  it  may  be  that  all  inheritance  may  be 
shown  to  do  this — there  is  no  real  or  permanent  blending,  of 
contrasted  qualities,  such  as  shortness  and  tallness,  black  and 
white,  rough  and  smooth,  etc.  Each  of  these  conditions  is 
considered  as  an  unmodifiable  persistent  unit  character  which 
can  be  combined  with  or  separated  from  others  but  cannot  be 
really  blended  with  any.  When  two  of  these  contrasted 
characters  are  brought  together  by  a  cross-mating  the  offspring 
of  this  mating  may  all  show  but  one  of  these  characters  or 
may  all  show  an  apparent  blending  of  them.  But  in  the  next 
generation,  obtained  by  mating  these  offspring  together,  or 
with  other  similarly  produced  offspring,  both  of  the  original 
contrasted  characters  will  reappear  and  by  proper  selecting 
and  mating  each  may  be  made  to  breed  pure  again.  If  the 
original  cross-mating  has  been  of  such  a  kind  as  to  bring 
together  several  different  pairs  of  contrasting  characters,  there 
will  be  opportunity  in  the  second  and  later  generations  to 
pick  out  individuals  showing  new  combinations  of  unit  char- 


340    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

acters  and  thus  representing  new  types  or  races.  This 
Mendelian  feature  of  the  combining  and  segregating,  recom- 
bining  and  resegregating  of  unchangeable  unit  characters,  has 
much  importance  for  the  practical  breeder.  It  is  a  condition 
depending  upon  the  character  of  the  germ  cells  produced  by 
the  mated  individuals  and  of  their  mated  offspring  rather 
than  of  the  somatic  or  general  bodily  character.  For  although 
after  the  first  cross-mating  all  of  the  offspring  may  be  like 
only  one  of  the  parents  as  regards  a  certain  character,  it  will 
be  found  that  by  allowing  them  to  produce  offspring  of  their 
own  that  their  germ  cells  really  represent,  in  presumably  equal 
numbers,  the  contrasted  characters  of  both  parents. 

The  Mendelian  order  of  heredity,  although  simple  and  easily 
understandable  in  its  more  apparent  aspects,  cannot  be  de- 
scribed in  a  few  words.  For  a  detailed  account  of  it  the  student 
should  read  some  such  modern  treatment  of  it  as  Punnett's 
"Mendelism,  "or  Bateson's  "Mendel's  Principles  of  Heredity." 

A  special  phase  of  the  problem  of  heredity  is  that  of  the  in- 
heritance of  acquired  characters.  The  congenital  characters 
of  an  individual,  which  are  the  outcome  of  the  constitution 
of  the  germ  cells  that  produced  it,  are  undeniably  heritable. 
Besides  these  characters,  however,  every  individual  acquires 
during  its  life  certain  characteristics  and  variations  which  are 
plainly  due  to  the  direct  modification  of  the  body  parts  and 
functions  by  its  lesser  or  greater  use  of  those  parts,  or  by  the 
direct  influence  of  the  abundance  or  scarcity  of  food,  the  rigor 
or  mildness  of  climate,  the  amount  of  sunlight  or  moisture, 
etc.  If  these  acquirements  on  the  part  of  the  parents  are 
heritable,  and  many  of  them  are  plainly  personal  adaptations 
to  the  particular  environment  and  circumstances  of  life  in 
which  the  individual  finds  himself,  then  inheritance  by  the 
offspring  would  be  a  distinct  advantage  in  leading  a  similar 
life.  If  they  could  start  endowed  at  birth  with  all  their 
parents  had  gained,  their  own  going  on  with  the  adapting  and 
modifying  process  would  lead  to  still  further  change  away  from 
the  original  type,  and  thus  in  comparatively  few  generations 
a  new  type  much  better  adapted  to  a  particular  kind  of 
environment  would  be  produced.  This  conception  of  personal 


ANIMAL  LIFE  AND  EVOLUTION  341 

acquirement  and  adaptation,  and  the  handing  on  of  it  by  in- 
heritance, resulting  in  a  rapid  cumulation  of  difference,  was 
the  basis  of  Lamarck's  explanation  of  evolution. 

But  owing  primarily  to  the  keenly  critical  examination  of 
the  actual  conditions  and  results  of  heredity  by  August  Weiss- 
mann,  present-day  biologists  believe  that  such  acquired  char- 
acters cannot  be  inherited,  and  hence  that  the  modification 
and  adaptation  of  species  has  all  to  depend  for  its  beginning 
on  favorable  chance  congenital  variations,  to  be  preserved 
and  slowly  cumulated  by  the  action  of  natural  selection. 
This  belief  makes  it  hard  to  gain  a  satisfactory  conception  of 
the  actual  methods  of  evolution,  because  it  makes  an  enormous 
demand  on  variation,  the  precise  working  of  selection,  and  the 
extent  of  geological  time.  So  that  there  is  a  strong  tendency 
among  present-day  biologists  to  search  for  other  factors  of 
species  modification,  and  to  try  to  determine  by  experiment 
the  actual  outcome  in  heredity  of  the  modification  of  the  body, 
and,  if  possible,  of  its  germ  cells,  by  external  influences.  As 
yet  none  of  these  experiments  has  given  any  sound  basis  for  a 
reinstatement  of  the  belief  in  the  inheritance  of  acquired 
characters,  but  some  of  them  do  prove  that  the  germ  cells  of 
animals  can  be  directly  influenced  by  external  conditions,  and 
that  young,  differing  markedly  from  their  parents,  are  produced 
by  these  influenced  germ  cells.  That  is,  environmental 
influences  which  may  modify  the  body  may  also  modify  the 
germ  cells  and  thus  cause  change  from  the  species  type  in  the 
offspring  which  can  be  handed  on  by  inheritance  to  their  own 
progeny,  but  these  changes  will  not  be  replicas  of  the  acquired 
variations  of  the  parents.  Thus  the  only  result  on  heredity 
of  a  better  exercise  of  an  animal's  capacities  will  be  to  give  its 
offspring  more  vigor  and  a  better  start  in  life  perhaps,  but  it 
cannot  endow  the  offspring  with  the  parents'  actual  gain  in 
fitness.  Education  can  be  handed  on  only  by  tradition,  not 
by  true  germinal  inheritance. 

Another  special  subject  in  connection  with  heredity  which 
should  be  mentioned  in  this  book  because  of  its  importance  in 
the  work  of  the  breeder,  is  that  of  the  alleged  advantage  or 
disadvantage  of  in-breeding.  In  the  light  of  the  Mendelian 


342    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

discoveries  in-breeding  is  seen  in  a  new  aspect.  The  mating 
together  of  closely  related  individuals  derives  both  its  ad- 
vantages and  disadvantages  from  the  probable  occurrence  in 
both  parents  of  similar  unit  characters.  Their  offspring 
will  thus  get  a  double  portion  of  each  common  character.  If 
it  is  a  good  trait  advantage  will  come  of  the  mating,  if  a  bad 
trait  disadvantage.  Thus  to  accent  and  fix  quickly  a  good 
trait  close  breeding  will  be  useful;  to  remove  a  bad  trait  out- 
breeding  will  be  necessary.  In  addition  out-breeding  practi- 
cally always  adds,  vigor  to  the  offspring.  But  in  many  cases 
of  in-breeding  vigor  is  not  lost  until  after  several  or  many  in- 
bred generations  have  been  produced. 

Selection,  Natural  and  Artificial. — Natural  selection,  which 
is  a  phrase  summing  up  the  presumable  result  of  the  interaction 
on  animals  and  plants  of  several  distinct  natural  causes  and 
conditions,  has  been  generally  considered  since  Darwin's  time 
to  be  the  principal  factor  in  evolution.  It  is  the  factor  chiefly 
relied  on  by  Darwin  in  his  explanation  of  evolution,  and  its 
formulation  is  Darwin's  principal  original  contribution  to 
evolutionary  discussion. 

Natural  selection  depends  upon,  first,  the  geometrical  ratio 
of  reproduction,  resulting  in  the  production  of  more  individuals 
than  there  is  food  or  space  for,  this  overproduction  of  living 
creatures  necessitating  a  "struggle  for  existence"  among  them; 
second,  the  universal  occurrence  of  variations,  small  or  large, 
among  all  the  myriads  born;  third,  the  presumption  that  some 
of  these  variations  will  give  advantages  to  certain  individuals 
in  this  struggle,  resulting  in  their  success  and  growth  to 
maturity  and  production  of  young;  fourth,  the  inheritance 
by  the  young  of  the  advantageous  variations  of  their  parents, 
and  their  handing  on  of  them  to  their  own  succeeding  genera- 
tions thus  constituting  a  new  race  or  species  characterized 
by  the  original  new  variations  and  succeeding  new  and  better 
ones.  Thus  there  is  a  "natural  selection"  of  individuals 
within  a  species,  and  also  a  "natural  selection"  of  specially 
favored  species  in  their  competition  with  other  species.  The 
whole  steadily  acting  combination  of  conditions  results  in  a 
constant  movement  from  one  kind  of  animal  or  plant  type  to 


ANIMAL  LIFE  AND  EVOLUTION  343 

another  and  to  the  establishment  of  divergent  lines  of  this 
movement,  these  changes  in  type  and  lines  always  being  in 
the  direction  of  better  adaptation  or  fitness  to  the  conditions 
of  life.  Several  recent  discoveries  based  upon  the  experi- 
mental study  of  variation  and  heredity  have  much  lessened 
the  importance  of  natural  selection  as  a  species-forming 
agent.  It  still  remains,  however,  the  chief  explanation  of 
adaptation. 

Artificial  selection  has  much  less  in  common  with  natural 
selection  than  popularly  supposed.  It  depends,  however,  as 
natural  selection  does,  upon  the  existence  of  variations  and 
heredity  and  upon  the  culling  out  of  certain  individuals  which 
are  allowed  to  produce  offspring  while  the  great  majority  are 
not  so  allowed.  This  culling  out,  or  selection,  however,  is  made 
according  to  the  needs  and  whims  of  man  and  not  at  all  upon 
the  basis  of  natural  advantage  or  fitness.  As  a  matter  of 
fact  most  artificial  selection  is  in  the  direction  of  unfitness 
for  existence  under  natural  conditions.  Very  few  domestic 
races  of  animals  could  hold  their  own  in  nature. 

In  artificial  selection,  man,  by  being  able  to  control  matings 
exactly,  has  a  means  of  modifying  races  much  more  rapidly 
than  they  are  usually  modified  in  nature.  Man  not  only  selects 
to  live  the  individuals  showing  certain  wished-for  variations, 
but  can  mate  together  individuals  which  show  these  particular 
variations  in  highest  degree.  Or  he  can  mate  individuals 
showing  different  variations  which  he  would  like  to  combine. 
By  taking  advantage  of  the  great  present-day  extension  of  our 
knowledge  of  the  facts  and  laws  of  variation,  inheritance,  and 
selection  the  artificial  breeder  can  work  much  more  rapidly 
and  with  much  more  accuracy  than  ever  before. 

Segregation,  or  Isolation. — The  modification  of  species 
either  in  nature,  or  under  the  hands  of  man,  always  includes  as 
part  of  the  process  the  segregation,  or  isolation,  from  the  whole 
mass  of  individuals  of  a  small  number  specially  like  each 
other.  This  is  effected  in  natural  selection  by  the  saving  of  the 
few  with  advantageous  variations  and  the  death  of  the  others; 
in  artificial  selection,  by  the  culling  out  process  of  the  breeder. 
These  few  saved  or  selected  individuals  breed  together  and  are 


344    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  beginners  of  a  new  type  within  the  species,  that  is,  of  a 
modification  of  it. 

Such  segregation  can  also  occur  in  nature,  and  certainly  often 
does,  by  the  chance  isolation  by  geographic  barriers  of  a  few 
individuals  of  a  species,  which  are  thus  prevented  from 
breeding  miscellaneously  with  the  other  members  of  the  species, 
but  must  breed  together,  thus  tending  to  perpetuate  their  own 
variations  and  idiosyncrasies.  Such  geographical  isolation 
has  certainly  led  to  the  origination  of  many  species  modifica- 
tions called  geographic  races  or  varieties,  and  with  time  and 
the  cumulation  of  these  modifications  through  many  genera- 
tions, to  many  actual  new  species. 

It  is  possible  also  that  certain  physiological  causes  of  the 
enforced  mating  together  of  certain  few  individuals,  thus  pro- 
ducing a  sort  of  physiological  segregation  or  isolation,  may  lead 
to  species  modification.  Personal  antipathies,  separate  times 
of  coming  to  maturity,  etc.,  may  act  as  such  agents  of  physi- 
ological segregation. 

The  Proof  of  Evolution. — Despite  our  statement  at  the  begin- 
ning of  this  chapter  that  the  fact  of  evolution  is  so  generally 
accepted  that  there  is  no  longer  any  discussion  of  its  proofs, 
it  may  be  advisable  to  state  here  succinctly  on  just  what  basis 
the  general  belief  in  evolution  rests.  This  basis  is  that  of  the 
observed  facts  in  four  general  biological  subjects,  namely, 
paleontology,  comparative  anatomy  and  physiology,  embry- 
ology and  development  (ontogeny),  and  plant  and  animal 
geography. 

By  a  study  of  animal  fossils  from  all  the  different  fossil- 
bearing  strata  of  the  earth's  crust,  it  is  evident  that  in  the 
earliest  geographical  epochs  only  very  simple  animals  lived, 
such  as  Protozoa,  the  simpler  invertebrates,  and,  perhaps,  a  few 
simple  Chordates.  With  the  passing  of  time  there  came  into 
existence  more  specialized  or  higher  invertebrates,  then  the 
simplest  true  vertebrates,  as  the  fishes  and  amphibians,  and 
finally  the  higher  kinds,  as  the  reptiles,  birds  and  mammals. 
The  paleontological  record  is,  in  other  words,  plainly  a  record 
of  organic  evolution. 

A  careful  comparison  of  the  structure  of  different  animals 


ANIMAL  LIFE  AND  EVOLUTION  345 

shows  such  fundamental  similarities  as  to  indicate  beyond 
doubt  an  actual  blood  relationship  of  wider  or  closer  degree 
among  them.  The  superficial  differences  among  animals 
evidently  of  common  identity  of  basic  structural  plan  are 
exactly  those  which  life  under  differing  conditions  would  call 
for  as  helpful  modifications  or  adaptations.  This  same  condi- 
tion of  fundamental  likeness  with  superficial  differences  is  true 
also  of  the  functions  or  physiology  of  animals. 

A  close  study  of  the  complete  life  history  or  development  of 
an  animal  from  beginning  egg  to  full-grown  adult  condition, 
reveals  the  fact  that  this  course  of  personal  development 
shows  striking  similarities  both  with  the  paleontological  record 
and  with  the  revelations  of  comparative  anatomy.  Ontogeny 
is  said  to  recapitulate  phylogeny,  by  which  is  meant  that  each 
animal  in  its  personal  development  runs  through  swiftly,  but 
more  or  less  obviously,  a  much  abridged  recapitulation  of  the 
stages  of  the  evolution  of  the  species  to  which  it  belongs. 

Finally  the  facts  of  the  present  and  past  distribution  of 
animals  over  the  earth's  surface  reveal  such  striking  conditions 
of  close  animal  relationships  accompanying  the  present  or  past 
continuity  of  land  and  water  masses,  and  such  wideness  of 
relationship  associated  with  long  separated  regions,  that  only 
the  explanation  of  evolution  is  sufficient  to  account  for  these 
facts.  In  Australia,  which  is  a  great  land  mass  long  separated 
geographically  from  other  continents,  the  animals,  except  such 
kinds  as  are  spread  by  man  unwittingly  or  intentionally,  or 
are  easily  distributed  by  ocean  currents,  are  of  kinds  very 
different  from  those  elsewhere  in  the  world.  But  in  Africa 
and  South  America,  which  are  more  widely  separated  geo- 
graphically but  have  been  connected  in  geological  periods  not 
so  very  remote,  there  are  many  fairly  close  relationships  among 
the  animals  of  the  two  regions.  The  differences,  also,  are  just 
about  as  great  as  the  length  of  time  of  the  actual  separation  of 
the  two  continents  would  make  probable.  By  such  zoo-geo- 
graphic studies  carried  on  for  many  kinds  and  groups  of  ani- 
mals, and  for  many  regions  of  the  earth,  a  great  army  of  facts 
has  been  collected  which  correspond  perfectly  with  the  theory 
of  descent,  i.e.,  evolution. 


346    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Animal  Ecology  and  Adaptations. — The  relation  of  animals 
to  their  physical  environment,  and  their  inter-relations  with 
other  animals  and  plants,  constitute  a  special  phase  of  biologic 
study  called  animal  ecology.  As  these  special  relations  are 
associated  always  with  special  adaptive  conditions  of  structure 
and  function,  the  subject  of  ecology  includes,  in  a  way,  the 
subject  of  adaptations,  and  thus  comes  with  particular  perti- 
nence under  the  attention  of  the  student  of  animal  evolution. 

The  relations  and  varied  adaptations  of  animals  in  connec- 
tion with  food  getting,  defense  and  offense,  production  and  care 
of  young,  and  similar  other  activities  common  to  all  animals 
but  performed  in  extraordinarily  various  ways,  are  most 
stimulating  subjects  of  investigation.  As  these  adaptations 
are  functional  as  well  as  structural,  such  subjects  include  the 
study  of  the  behavior,  instincts  and  intelligence  of  animals,  and 
become  thus  directly  related  to  the  problem  of  the  origin  of  our 
own  instincts  and  intelligence.  Among  the  various  highly 
developed  special  adaptations  of  animals  those  of  color  and 
color  pattern,  of  parasitism,  and  of  different  phases  of  mutual 
aid,  offer  unusually  interesting  subjects  of  special  study,  and 
may  be  introduced  here  by  a  few  paragraphs. 

Color  is  produced  by  the  presence  of  pigment  in  the  surface 
parts  or  by  the  structural  character  of  the  epidermal  hairs, 
feathers,  or  scales  with  which  the  animal's  body  may  be 
covered.  By  reflection  and  interference  effects,  due  to  the 
laminated  or  striated  structure  of  these  parts,  brilliant  metallic 
or  iridescent  colors  are  produced,  such  as  the  blues,  purples  and 
greens  of  the  humming-birds,  butterflies,  fishes,  etc.  The 
most  obvious  use  of  the  colors  depends  largely  upon  their 
arrangement  into  definite  patterns  and  on  the  harmonizing  of 
these  color  patterns  with  the  environment  in  such  a  way  as  to 
make  the  animal  more  or  less  indistinguishable  when  at  rest 
and  thus  hide  it  from  its  enemies.  The  phenomena  of  pro- 
tective resemblance  and  mimicry  are  among  the  most  highly 
developed  and  extraordinary  of  animal  adaptations. 

Some  of  the  many  curious  conditions  of  structure,  develop- 
ment and  habit,  developed  in  connection  writh  the  adoption  of  a 
parasitic  life  have  already  been  described  in  this  book. 


ANIMAL  LIFE  AND  EVOLUTION  347 

Another  kind  of  association  among  animals  is  that  based  on  a 
greater  or  lesser  degree  of  mutual  aid  derived  from  this  associa- 
tion. It  appears  in  two  types,  one  exemplified  by  com- 
mensalism  and  symbiosis,  in  which  two  different  kinds  of 
animals  live  together  temporarily  or  permanently  to  their 
mutual  benefit  or  at  least  to  the  benefit  of  one  kind  and 
little  or  no  injury  to  the  other,  and  the  other  exemplified  by  a 
gregarious  and  social  or  communal  life,  in  which  a  number  of 
individuals  of  the  same  kind  live  together  in  temporary  or 
permanent  bands  or  in  large  family  communities. 

The  first  type  is  illustrated  by  the  hermit  crabs  that  carry 
colonies  of  hydroid  polyps  on  their  shells,  the  little  crab  being 
protected  from  enemies  by  the  stinging  threads  of  the  polyps, 
while  the  sessile  polyps  gain  an  advantage  by  the  crab's 
movements  and  probably  by  getting  small  bits  from  the  crab's 
clumsy  tearing  up  of  its  own  food.  Especially  developed  is 
the  commensal  relation  between  certain  insects  called  ant- 
guests  and  the  ants  which  serve  as  their  hosts.  Over  1500 
species  of  insects,  mostly  small  beetles  and  flies,  live  in  the 
nests  of  various  ants,  some  as  robbers,  some  as  tolerated  para- 
sites, and  some  as  desired  commensals.  These  latter  provide 
the  ants  with  certain  kinds  of  special  food  produced  by  their 
bodies,  and  aid  in  cleaning  both  the  nests  and  the  ants  them- 
selves, while  they  in  turn  receive  food  from  the  storerooms  of 
the  ants,  or  even  by  regurgitation  from  their  mouths. 

Of  the  second  type  the  life  of  the  communities  of  the  social 
wasps  and  bees  and  ants,  already  described  in  some  detail 
elsewhere  in  this  book,  is  the  best  example.  The  highly 
specialized  communities  of  the  honey-bee  and  of  the  ants  are 
a  splendid  illustration  of  the  possibilities  and  great  advantages 
of  adaptations  based  on  the  principle  of  mutual  aid.  It  is 
of  course  the  extreme  development  of  the  mutual  aid  factor 
in  human  life  that  makes  man  the  highly  successful  and  noble 
animal  he  is. 


PART  II 


CHAPTER  XXVIII 

PARASITIC  PROTOZOA  CAUSING  DISEASES  OF  MAN 
AND  DOMESTIC  ANIMALS 

Parasites  and  Disease. — More  than  two  hundred  years 
ago  it  was  known  that  small  animal  parasites  were  associated 
with  and  were  the  cause  of  certain  diseases,  and  it  soon  came 
to  be  generally  believed  that  all  of  our  ills  were  in  some  way 
caused  by  such  parasites,  known  or  unknown.  At  first  only  the 
parasitic  worms  and  other  large  parasites  were  known,  but 
later  it  was  discovered  that  many  of  the  Protozoa  and  minute 
plant  parasites,  the  bacteria,  also  caused  many  diseases.  To- 
day we  know  definitely  that  such  diseases  as  typhoid,  cholera, 
tuberculosis  and  many  others  are  caused  by  the  presence  of 
bacteria  in  the  body  and  that  such  maladies  as  malaria, 
sleeping  sickness,  syphilis,  and  many  fevers  are  caused  by 
Protozoa. 

Then  there  is  a  long  list  of  other  epidemic  diseases,  such  as 
smallpox,  measles  and  scarlet  fever,  the  exact  cause  of  which 
has  not  been  determined.  Many  of  these  are  believed  to  be 
due  to  micro-organisms  of  some  kind,  and  if  so  these  parasites 
will  almost  certainly  sooner  or  later  be  found.  Curiously 
enough  most  of  the  diseases  in  this  last  class,  and  many  of  those 
that  are  caused  by  bacteria,  are  contagious,  while  all  that  are 
caused  by  animal  parasites  are,  as  far  as  is  known,  infectious 
but  not  contagious.  It  is  important  that  we  keep  in  mind  this 
distinction.  By  contagious  diseases  are  meant  those  which 
are  transmitted  by  contact  with  the  diseased  person,  by  touch, 
or  by  the  breath  or  the  effluvia  from  the  body,  or  by  the  use 

349 


350    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

of  the  same  articles.  Smallpox,  measles  and  influenza  are 
examples  of  this  group.  By  infectious  diseases  are  meant  those 
which  are  disseminated  by  contaminated  water  or  food,  or  other 
infected  substances  introduced  into  the  body  in  some  way. 
Typhoid,  malaria,  yellow  fever,  and  cholera,  and  others  are 
examples  of  this  class.  Thus  it  is  evident  that  all  of  the  con- 
tagious diseases  may  be  infectious,  but  most  of  the  infectious 
diseases  are  not  as  a  rule  contagious,  although  some  of  them 
may  become  so  under  favorable  conditions. 

Just  one  example  will  show  the  importance  of  knowing 
whether  a  disease  is  contagious  or  infectious.  Until  a  few  years 
ago  it  was  believed  that  yellow  fever  was  highly  contagious, 
and  every  precaution  was  taken  to  keep  the  disease  from 
spreading  by  keeping  the  infected  region  in  strict  quarantine. 
This  often  meant  much  hardship  and  suffering  and  always  a 
great  financial  loss.  We  now  know  that  it  is  infectious  only 
and  not  contagious,  and  that  all  this  quarantine  was  unnec- 
essary. The  whole  fight  in  controlling  an  outbreak  of  yellow 
fever,  or  in  preventing  such  an  outbreak,  is  now  directed  against 
the  mosquito,  the  sole  agent  by  which  the  disease  can  be  trans- 
mitted from  one  person  to  another. 

Definition  of  a  Parasite. — A  parasite  is  a  living  organism 
that  lives  in  or  on  some  other  organism  from  which  it  derives 
its  nourishment  for  the  whole  or  a  part  of  its  existence.  As  a 
general  thing  we  are  accustomed  to  think  of  a  parasite  as  work- 
ing more  or  less  injury  to  its  host.  As  a  matter  of  fact  the  num- 
ber of  parasitic  organisms  that  are  seriously  detrimental  to 
the  welfare  of  their  hosts  is  comparatively  small  while  the 
number  of  parasites  that  do  no  appreciable  harm,  and  of  whose 
existence  in  the  body  the  host  is  often  not  even  aware,  is  large. 

DISEASES  CAUSED  BY  AMCEB.E 

Amoebic  Dysentery. — A  species  of  Amoeba,  A.  dysenteries,  is 
found  associated  with  a  disease  of  man  known  as  amoebic 
dysentery.  This  disease  occurs  most  commonly  in  tropical 
countries,  but  is  sometimes  met  with  in  temperate  zones. 
The  amceba3  are  found  in  the  alimentary  canal,  usually  in 


PARASITIC  PROTOZOA  351 

the  large  intestine,  where  they  produce  serious  ulcers  or 
at  least  extend  and  prevent  the  healing  of  ulcers  started  from 
other  causes.  Amoeboid  organisms  are  found  in  the  tissues 
of  the  brain  in  animals  affected  with  hydrophobia,  and 
similar  organisms  are  found  in  the  skin  of  smallpox  patients, 
but  it  has  not  been  shown  that  they  cause  these  diseases. 
Several  other  Amcebce  may  be  found  in  various  tissues  or 
organs  of  men  and  many  of  the  domestic  animals,  but  they 
are  usually  regarded  as  harmless. 

One  species,  Amoeba  meleagridis ,  is,  however,  the  cause  of  a 
fatal  disease  of  turkeys  known  as  entero-hepatitis,  or  "black- 
head." The  disease  is  now  spread 
throughout  North  America,  and  when 
once  a  farm  has  become  infected  no 
further  attempts  should  be  made  to 
raise  turkeys  there,  at  least  for  some 
years.  Turkeys  become  infected  by 
swallowing  the  encysted  amoebae  that 
have  been  distributed  in  the  drop- 
pings from  infested  turkeys.  Young 
turkeys  may  become  infected  from  FlG  I4?Z Amoeba dysen- 
encysted  amoeba?  which  adhere  to  teria.  The  two  lower  para- 
the  shells  from  which  they  hatch.  *£$££*$?  ™£ 
In  the  alimentary  canal  of  their  host  smaller  spherical  mass  in 
the  amoebae  break  from  their  cyst  and  the  upper  left  corner  is  an 
cause  ulceration  of  the  intestine  and 
abscess  of  the  liver.  Diarrhea  soon 
begins,  and  in  the  later  stages  of  the  illness  the  head  of  the 
turkey  turns  black. 

The  same  Amoeba  often  occurs  in  other  birds,  such  as  chick- 
ens, ducks,  quail,  pigeons,  sparrows,  etc.,  but  it  seldom  causes 
serious  trouble  in  any  except  turkeys,  and  young  turkeys  are 
much  more  susceptible  than  old  ones.  It  is  believed  that 
sparrows  have  been  an  important  factor  in  the  spread  of  the 
disease. 

There  is  no  efficient  remedy.  Turkeys  should  not  be 
allowed  to  run  with  other  fowls  and  they  should  be  kept  only 
in  uninfected  places. 


352    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


SLEEPING  SICKNESS  AND  OTHER  DISEASES  CAUSED  BY 
TRYPANOSOMES 

To  the  group  of  parasitic  Protozoa  known  as  trypanosomes 
belong  some  of  the  most  important  enemies  of  mankind. 
These  elongated,  spindle-shaped,  delicate  little  organisms,  are 
found  in  insects,  reptiles,  birds  and  mammals.  Many  of  the 
most  important  species  are  conveyed  from  one  vertebrate  host 
to  another  by  means  of  insects,  the  parasites  often  undergoing 
some  stages  of  their  development  in  the  invertebrate  host. 


FIG.  148. — Trypanosoma  gambiense.     Various  forms  from  blood  and  cere- 
brospinal  fluid.     (After  Manson.) 

Trypanosoma  lewisi,  a  parasite  of  rats,  is  perhaps  the 
best  known,  as  it  is  always  common  wherever  rats  are  found. 
These  parasites  are  transmitted  from  rat  to  rat  by  the  common 
rat-louse  and  probably  also  by  rat-fleas.  They  do  not  seem 
to  injure  the  rats.  Trypanosoma  gambiense  is  the  most 
important  member  of  this  group,  as  it  is  the  parasite  that 
causes  the  disease  known  as  sleeping  sickness,  a  scourge 
that  for  the  last  few  years  has  created  more  interest  and 


PARASITIC  PROTOZOA 


353 


been  more  carefully  studied  than  any  other  disease.  It 
has  spread  rapidly  over  a  large  part  of  Africa,  killing  hundreds 
of  thousands  of  the  natives  of  these  regions.  The  early  symp- 
toms of  the  disease  are  various,  but  infection  is  usually  soon 
followed  by  fevers,  and  the  patient  gradually  becomes  anemic 
and  physically  and  intellectually  feeble,  with  an  increasing 
tendency  to  sleep.  As  the  stupor  deepens  the  patient  loses 
all  desire  or  power  of  exertion  and  soon  succumbs  to  the 
uncanny  death. 

Other  animals  beside  man  may  be  infected  with  this  parasite, 
but  it  does  not  seem  to  injure  them.     The  parasite  is  carried 


FIG.  149. — Tsetse-fly.     (After  Manson;  two  and  one-fourth  times  natural 

size.) 


from  one  host  to  another  by  a  species  of  tsetse-fly,  Glossina 
palpalis,  which  resembles  somewhat  our  common  stable-fly. 
It  is  now  known  that  another  tsetse-fly,  G.  morsitans,  is 
also  an  agent  in  the  transmission  of  this  disease.  When  the 
fly  sucks  blood  from  an  infected  animal  some  of  the  trypano- 
somes  are  taken  into  its  body  where  they  undergo  certain 
changes,  the  fly  usually  not  becoming  infective  until  about 
three  or  four  weeks  later.  It  is  then  capable  for  a  period  of 

23 


354    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

four  months  or  more  of  infecting  any  person  or  other  animal 
that  it  bites. 

G.  palpalis  is  found  only  in  tropical  Africa  and  is  limited  in  its 
distribution  there  to  certain  very  definite,  narrow,  brushy 
areas  along  the  water's  edge.  If  these  places  can  be  avoided 
there  seems  to  be  little  danger.  Those  who  are  fighting  the 
disease  have  found  that  if  the  brush  in  the  vicinity  of  watering- 
places  and  ferry-landings  is  cleared  away  such  places  become 
comparatively  safe.  These  flies  do  not  lay  eggs  but  produce 
full-grown  larvae  which  soon  pupate  in  the  ground. 

Trypanosoma  cruzi  is  another  species  that  causes  a  serious, 
often  fatal,  disease  in  Brazil.  It  is  transmitted  by  the  bug 
Conorrhinus  megisius,  belonging  to  the  family  Reduviidce,  order 
Hemiptera.  This  bug  has  habits  very  similar  to  those  of  the 
bedbug,  inhabiting  houses  and  biting  sleeping  persons.  Kala 
azar,  a  chronic  disease  occurring  in  the  Mediterranean  region 
and  in  many  places  in  Asia,  is  caused  by  a  parasite,  Leish- 
mannia  donovani,  somewhat  resembling  the  trypanosomes. 
The  infection  is  probably  acquired  by  the  biteiof  an  insect, 
perhaps  a  bedbug.  A  similar  disease,  called  Delhi  boil,  occurs 
in  the  same  region  and  also  in  Brazil,  and  it  is  thought  that 
infection  may  be  carried  to  a  wound  by  house-flies. 

There  are  several  diseases  of  domestic  animals  caused  by 
trypanosomes.  Tsetse-fly  disease,  or  nag  ana,  is  one  of  the 
most  serious  scourges  of  domestic  animals  in  Central  and 
Southern  Africa.  In  some  sections  it  is  almost  impossible  to 
keep  any  kind  of  imported  animals  on  account  of  this  disease, 
which  is  caused  by  Trypanosoma  brucei.  This  parasite  is  to 
be  found  in  several  different  kinds  of  native  animals  which  seem 
to  be  themselves  practically  immune  but  are  always  a  source 
of  danger  when  non-immune  animals  are  introduced.  The 
tsetse-fly,  Glossina  morsitans,  one  of  the  most  dreaded  insect 
pests  of  Southern  Africa,  is  largely  responsible  for  the  trans- 
mission of  this  disease,  but  one  or  two  other  species  of  tsetse- 
flies  may  also  act  as  hosts  for  the  parasite.  All  through  Asia, 
in  parts  of  Africa  and  in  the  Philippines  there  is  a  very  serious 
disease  of  horses  and  cattle  known  as  surra.  This  disease, 
which  also  affects  camels,  elephants,  buffaloes  and  dogs  in 


PARASITIC  PROTOZOA  355 

regions  where  it  occurs,  is  caused  by  Trypanosoma  evansi  and 
is  probably  transmitted  by  the  bites  of  stable-flies  (Stomoxys) 
and  horse-flies  (Tabanida). 

In  1906  some  cattle  that  had  been  imported  into  America 
from  India  for  experimental  purposes  were  found  to  be  in- 
fected by  the  parasite  which  causes  this  disease.  Fortunately 
this  discovery  was  made  while  the  cattle  were  still  in  quaran- 
tine. All  those  infected  were  destroyed  and  the  disease  thus 
stamped  out  before  it  had  a  chance  to  spread.  A  disease 
similar  to  both  nagana  and  surra,  and  known  as  murrina,  has 
recently  been  found  affecting  horses  and  mules  in  Panamas. 
It  is  caused  by  Trypanosoma  hippicum.  It  is  believed  that  the 
parasite  is  carried  mechanically  from  one  host  to  another  by 
flies  that  visit  the  sores  due  to  wounds  of  various  kinds  on  the 
animals. 

Dourine,  or  mal  du  coit,  is  a  serious  disease  of  horses  that 
has  been  introduced  into  North  America,  where  it  appears  from 
time  to  time  in  widely  separated  parts  of  the  west.  It  is  caused 
by  Trypanosoma  equiperdum,  and  is  transmitted  during  breed- 
ing, perhaps  rarely  by  bites  of  flies  or  fleas.  As  soon  as  infect- 
ed animals  are  discovered  they  are  destroyed,  and  the  disease 
is  now  almost  or  quite  stamped  out.  Trypanosoma  equinum 
causes  a  deadly  disease  of  horses,  known  as  mal  de  caderas,  in 
Brazil  and  other  parts  of  South  America. 

Several  other  species  of  trypanosomes  are  found  in  wild  and 
domestic  animals.  Almost  any  of  these  may  at  any  time  be- 
come of  more  or  less  economic  importance  when  susceptible, 
non-immune  animals  are  brought  into  the  regions  where  the 
parasites  occur,  or  when  the  parasites  by  some  means  are 
introduced  into  new  regions. 

RELAPSING  FEVERS  AND  OTHER  DISEASES  CAUSED  BY 
SPIROCH,ETES 

The  spirochsetes  are  very  minute,  thread-like  parasites 
closely  related  to  the  trypanosomes.  They  occur  in  shellfish 
and  in  the  alimentary  canal  or  blood  of  certain  fish,  birds  and 
mammals  where  they  apparently  do  no  harm,  but  some 


356    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

produce  diseases  in  man   and  other  animals.     The  most  im- 
portant of  these  are  the  relapsing  fevers  of  which  there  are 


FIG.  150. — Relapsing   fever   tick,    Ornithodorus    moubala.     (About    four 
times  natural  size.) 


FIG.  151. — The  fowl-tick,  Argas  persicus.    (About  four  times  natural  size.) 


several  types  caused  by  as  many  different  species  of  Spiro- 
chceta.     The  relapsing  fever  of  Africa,  or  African  tick  fever, 


PARASITIC  PROTOZOA  357 

is  one  of  the  most  dreaded  of  these.  It  is  caused  by  S.  dutioni, 
and  is  transmitted  by  the  bite  of  a  common  African  tick, 
Ornithodorus  moubata,  which  has  habits  similar  to  those  of  the 
bedbug.  The  relapsing,  or  remittent  fever  of  Europe  is  caused 
by  S.  recurrentis,  and  is  probably  transmitted  by  some  blood- 
sucking insect,  possibly  by  the  bedbugs.  The  relapsing  fever 
of  America  is  caused  by  5".  novyi.  The  mode  of  infection  is  not 
definitely  known.  Yaws,  a  disease  of  the  tropics  which  is 
characterized  by  numerous  ulcerating  sores  on  the  body,  is 
caused  by  Spirochata  pallidula.  It  is  thought  that  the  common 
house-fly  plays  an  important  part  in  its  dissemination.  Of  the 
diseases  of  domestic  animals  caused  by  spirochsetes  a  fatal 
disease  of  fowls  known  as  spirochaetosis  is  the  most  important, 
as  it  may  kill  all  the  fowls  in  the  chicken  yard  in  the  course  of  a 
few  days.  It  is  caused  by  Spirochada  marchouxi  (gallinarum) 
and  is  transmitted  by  ticks,  usually  by  the  common  chicken 
tick,  Argas  persicus. 

Syphilis. — To  the  genus  Treponema  belongs  a  single  im- 
portant parasite,  T.  pallidum,  that  used  to  be  classed  with  the 
Spirochceta.  It  is  the  cause  of  that  terrible  disease,  syphilis, 
which  results  in  untold  suffering  not  only  among  those  individ- 
uals who  are  responsible  for  its  dissemination  but  among  many 
innocent  persons  as  well.  Much  of  the  syphilitic  disease  that 
is  in  the  world  to-day  is  due  to  the  infection  of  infants  before 
or  at  the  time  of  their  birth. 

MALARIAL  FEVERS  AND  OTHER  DISEASES  CAUSED  BY  SPOROZOA 

The  Sporozoa,or  spore-forming  Protozoa,  include  the  smallest 
but  by  no  means  least  important  members  of  the  branch. 
They  are  all  parasitic  and  vary  greatly  in  appearance,  organiza- 
tion and  life  history.  They  are  so  very  plastic  that  they  can 
adapt  themselves  readily  to  their  various  hosts.  Some  of 
them  live  during  some  stages  of  their  development  in  the  blood 
cells  of  man  and  other  vertebrates,  the  rest  of  their  life  being 
passed  in  insects  or  other  invertebrates.  Malarial  fevers  are 
caused  by  such  parasites.  Those  that  occur  in  man  belong  to 
the  genus  Plasmodium.  The  three  most  important  species  are 


358 


ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

2. 


Some  may  be  taken 
into  the  stomach 
of  the  Hlosquito  w'nen 
it  bites 


& 

FIG.  152. — Diagram  to  illustrate  the  life-history  of  the  malarial  para- 
site, i  is  a  red  blood  corpuscle;  2  to  7  show  the  development  of  the 
parasite  in  the  corpuscle;  abed  and  a'  V  c'  and  e  the  development  of  the 
parasite  in  the  stomach  of  the  mosquito;  /  g  h  i  the  development  in  the 
capsule  on  the  outer  wall  of  the  stomach  of  the  mosquito,  k  in  the  salivary 
gland. 


PARASITIC  PROTOZOA  359 

vivax,  malaria  and  falciparum,  causing  respectively  the  tertian, 
quartan  and  remittent  types  of  malarial  fever  in  man. 

The  life  history  of  all  of  these  is  very  similar,  the  principal 
difference  being  in  the  length  of  time  it  takes  them  to  sporulate. 
Let  us  begin  with  the  parasite  after  it  has  been  introduced  into 
the  blood  and  trace  its  development  there.  At  first  it  is  slender 
and  rod-like  in  shape.  It  has  some  power  of  movement  in  the 
blood-plasma.  Very  soon  it  attacks  one  of  the  red  blood- 
corpuscles  and  gradually  pierces  its  way  through  the  wall  and 
into  the  corpuscle  substance;  here  it  becomes  more  amoeboid 
and  continues  to  move  about,  feeding  all  the  time  on  the 
corpuscle  substance,  gradually  destroying  the  whole  blood 
cell.  As  the  parasite  feeds  and  grows  there  is  deposited  within 
its  body  a  blackish  or  bro\vnish  pigment  known  as  melanin. 

During  the  time  that  the  parasite  is  feeding  and  growing  it 
is  also  giving  off  waste  products,  but  as  the  parasite  is  com- 
pletely inclosed,  in  the  corpuscle  wall  these  waste  products 
cannot  escape  until  the  wall  bursts.  After  about  forty  hours, 
if  the  parasite  is  vivax,  or  about  sixty-five  hours  if  it  is  malaria, 
it  becomes  immobile,  the  nucleus  divides  again  and  again  and 
the  protoplasm  collects  around  these  nuclei,  forming  a  number 
of  small  cells,  or  spores,  as  they  are  called.  In  about  forty- 
eight  or  seventy-two  hours,  depending  on  whether  the  parasite 
is  vivax  or  malaria,  the  wall  of  the  corpuscle  bursts  and  all  these 
spores  with  the  black  pigment  and  the  waste  products  that 
have  been  stored  away  within  the  cell  are  liberated  into  the 
blood-plasma. 

These  spores  are  round  or  somewhat  amoeboid  and  are  carried 
in  the  blood-plasma  for  a  short  time.  Very  soon,  however, 
each  one  attacks  a  new  red  corpuscle  and  the  process  of 
feeding,  growth  and  spore-formation  continues,  taking  exactly 
the  same  time  for  development  as  in  the  first  generation,  so  that 
every  forty-eight  hours  in  the  case  of  vivax,  and  every  seventy- 
two  hours  in  the  case  of  malaria,  a  new  lot  of  these  spores  and 
the  accompanying  waste  products  are  thrown  out  into  the 
blood.  Thus  in  a  very  short  time  many  generations  of  this 
parasite  occur,  and  thousands  or  hundreds  of  thousands  of  the 
red  blood  corpuscles  are  destroyed,  leaving  the  patient  weak 


360    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  anaemic.  It  will  be  seen,  too,  that  the  recurrence  of  the 
chills  and  fevers  is  simultaneous  with  the  escaping  of  the 
parasites  from  the  blood  corpuscles,  together  with  the  waste 
products  of  their  metabolism.  These  waste  products  are 
poisonous,  and  it  is  believed  that  this  great  amount  of  poison 
poured  into  the  blood  at  one  time  causes  the  regular  recurring 
crisis. 


FIG.  153. — Malarial   mosquito,    Anopheles   maculipennis,    on   the   wall. 
(About  six  times  natural  size.) 

We  have  already  learned  that  such  a  process  of  asexual  re- 
production cannot  go  on  indefinitely,  but  for  a  long  time  those 
who  were  studying  these  parasites  were  at  a  loss  to  know  where 
the  sexual  stage  took  place.  Many  men  have  worked  on  this 
problem  but  perhaps  most  .credit  will  always  be  given  to 
Ronald  Ross,  a  surgeon  in  the  English  army,  who,  after  many 
months  of  continuous  labor,  finally  demonstrated  that  the 


PARASITIC  PROTOZOA  361 

sexual  stage  of  the  development  of  these  parasites  takes  place 
in  the  stomach  of  the  mosquito. 

It  was  found  that  certain  of  the  parasites  in  the  blood  do  not 
go  on  with  their  development  there.  When  these  particular 
parasites  are  taken  into  the  stomach  of  most  mosquitoes  they 
are  digested  with  the  rest  of  the  blood.  But  when  they  are 
taken  into  the  stomach  of  mosquitoes  belonging  to  the  genus 
Anopheles,  or  other  closely  related  genera,  they  are  not  digested 
but  go  on  with  their  development.  Conjugation  takes  place, 
resulting  in  the  production  of  a  new  form  of  the  parasite,  the 
zygote,  that  makes  its  way  through  the  walls  of  the  stomach  on 
the  outside  of  which  it  forms  a  little  nodule.  Within  these 
nodules  further  division  and  development  takes  place,  until 
finally  the  nodules  burst  open  and  many  thousand  minute  rod- 
like  organisms,  sporozoites,  formed  by  the  repeated  division 
of  the  zygote,  are  turned  loose  into  the  body  cavity  of  the 
mosquito.  Owing  to  some  unknown  cause  these  little  organ- 
isms collect  in  the  large  vacuolated  cells  of  the  salivary  glands 
of  the  mosquito,  and  when  the  mosquito  bites  a  man  they  pour 
down  through  the  ducts  with  the  secretion  into  the  beak 
and  are  thus  again  introduced  into  the  human  circulation. 

The  nodules,  or  cysts,  on  the  walls  of  the  stomach  of  the 
mosquito  may  contain  as  many  as  ten  thousand  sporozoites, 
and  as  many  as  five  hundred  cysts  may  occur  on  a  single 
stomach. 

It  takes  ten,  twelve,  or  more  days  from  the  time  the  parasites 
are  taken  into  the  stomach  of  the  mosquito  before  they  can 
complete  their  transformations  and  reach  the  salivary  gland, 
the  time  depending  on  the  temperature.  So  it  is  ten  or  twelve 
days,  or  sometimes  as  long  as  eighteen  or  twenty  days,  from  the 
time  an  Anopheles  bites  a  malaria]  patient  before  it  is  dangerous 
or  can  spread  the  disease.  On  the  other  hand,  the  sporozoites 
may  lie  in  the  salivary  gland  alive  and  virulent  for  several 
weeks.  It  does  not  give  up  all  the  parasites  at  one  time,  so  that 
three  or  four  or  more  people  may  be  infected  by  a  single 
mosquito. 

The  findings  of  Ross  have  been  verified  many  times,  and 
many  experiments  have  proven  beyond  any  doubt  that  this  is 


362    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


the  only  way  in  which  malaria  is  transmitted,  and  that  the 
low-lying  lands  or  swamps  have  nothing  whatever  to  do  with 
malaria  except  in  so  far  as  they  furnish  a  breeding  place  for 
mosquitoes.  Much  less,  then,  can  the  mists  or  bad  air — -mal 
aria  in  the  Italian — produce  malaria.  Without  mosquitoes 
there  is  no  malaria. 

TEXAS  FEVER  or  CATTLE 

To  the  genus  Babesia  (formerly  known  as  Piro plasma)  be- 
long several  species  of  blood  parasites  that  are  of  great  eco- 
nomic importance.  In  the  vertebrate  host  they  live  in  the 


FIG.  154.- 


-Texas  fever   tick,    Margaropus   annulatus,    young   adult   not 
fully  gorged.     (About  four  times  natural  size.) 


red  blood  corpuscles,  and  they  are  transmitted  from  one 
animal  to  another  by  means  of  ticks.  The  most  important  of 
the  diseases  caused  by  the  members  of  this  genus  is  a  disease 
of  cattle  known  in  the  United  States  as  Texas  fever,  or  tick 
fever,  or  splenic  fever.  It  occurs  in  nearly  all  tropical  and 
subtropical  and  in  many  temperate  regions,  and  outside  of 
the  United  States  is  more  commonly  known  as  "red  water." 
In  the  United  States  it  causes  an  annual  loss  estimated  at  $100,- 


PARASITIC  PROTOZOA  363 

000,000,  and  in  many  parts  of  the  world  it  is  almost  impossible 
to  keep  cattle  because  such  a  large  per  cent,  of  them  die  of 
the  disease.  The  parasite,  Babesia  bigeminum,  that  causes  the 
disease  is  transmitted  by  the  common  cattle  tick,  or  Texas 
fever  tick,  Mar  gar  opus  annulatus,  in  the  United  States,  and  by 
closely  related  species  in  other  countries.  The  infection  is  not 
direct,  that  is,  the  tick  does  not  feed  on  one  host,  then  pass 
directly  to  another,  carrying  the  disease  germs  with  it.  Unlike 
many  other  ticks  the  Texas  fever  tick  does  not  leave  its  host 
until  it  is  fully  developed.  When  the  female  is  full  grown 
and  gorged  she  drops  to  the  ground  and  lays  from  1000  to 
4000  eggs  from  which  the  minute  "seed  ticks"  soon  hatch. 
These  make  their  way  to  some  nearby  blade  of  grass  or  shrub 
and  at  the  first  opportunity  attach  themselves  to  any  cattle 
that  may  pass  that  way. 

If  the  mother  tick  feeds  on  an  animal  that  is  infected  with 
Texas  fever  some  of  the  parasites  that  she  takes  into  the  body 
will  find  their  way  into  her  eggs,  and  the  young  ticks  that  hatch 
from  these  will  be  infected  and  ready  to  transmit  the  disease 
to  their  host. 

It  has  been  found  that  the  Southern  cattle  in  the  regions 
where  the  ticks  occur  normally  usually  have  a  mild  attack  of 
the  disease  when  they  are  young,  and  although  they  may  be 
infected  with  the  parasite  all  the  rest  of  their  life  it  does  not 
affect  them  seriously.  But  these  cattle  are  a  source  of  danger 
when  taken  into  a  region  where  the  ticks  do  not  occur  naturally, 
for  the  larvae  that  issue  from  the  eggs  laid  by  the  infected  adult 
ticks  may  attack  non-immune  cattle  which  soon  sicken  and  die. 

At  present  in  the  United  States  no  cattle  south  of  a  certain 
quarantine  line  are  allowed  to  be  taken  north  except  under 
very  strict  regulations.  It  has  been  demonstrated  that  by  a 
system  of  feed-lots  and  pasture  rotation  many  infested  regions 
may  be  made  perfectly  safe.  The  aim  is  to  let  all  of  the  ticks 
drop  to  the  ground  on  land  where  they  may  be  destroyed  or 
left  to  starve.  When  it  is  necessary  to  treat  cattle  that  are 
badly  infested  with  ticks,  large  vats  are  built  and  filled  with  a 
dipping  solution  and  the  cattle  are  then  driven  through  it. 
Many  different  kinds  of  solutions  have  been  used  for  this  pur- 


364    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

pose.  One  should  consult  some  of  the  Government  or  Experi- 
ment Station  Bulletins  (see  page  419)  for  directions  for  making 
and  using  these. 

Similar  diseases  caused  by  other  species  of  the  genus  Babesia 
occur  in  horses,  sheep,  dogs  and  other  animals,  but  none  is  so 
important  as  the  Texas  fever  of  cattle. 

OTHER  PROTOZOAN  DISEASES 

Spotted  Fever. — Spotted  fever,  or  Rocky  Mountain  fever, 
is  a  disease  that  occurs  in  the  mountains  in  the  northwestern 
United  States.  It  is  transmitted  by  ticks,  Dermacentor  ven- 
ustus,  and  is  supposed  by  many  to  be  due  to  an  organism  closely 
related  to,  or  belonging  to  the  genus  Babesia.  It  has  been 
shown  that  domestic  animals,  particularly  the  larger  ones, 
in  the  region  where  the  fever  occurs,  are  the  principal  hosts 
for  the  adult  ticks,  so  if  these  animals  can  be  kept  free  from 
ticks,  by  dipping  and  otherwise,  the  disease  can  be  largely 
controlled. 

Pebrine  of  Silkworms. —About  the  middle  of  the  nine- 
teenth century  a  strange  malady  appeared  among  the  silk- 
worms in  Southern  France  and  caused  enormous  losses.  The 
silk  growers  knew  nothing  of  the  nature  of  the  disease,  and  were 
at  a  loss  to  know  how  it  spread,  for  even  though  they  placed 
the  eggs  of  the  silk-worm  moth  in  perfectly  clean  places  and 
took  the  very  best  care  of  the  larvae,  the  silk-worms  would 
suddenly  sicken  and  die  at  a  certain  stage  of  their  development. 
Pasteur,  who  was  then  just  beginning  his  great  work,  made  a 
careful  study  of  the  disease  and  discovered  that  it  was  caused 
by  a  sporozoan.  It  was  found  that  this  parasite,  now  known 
as  Glugea  (Nosema)  bombycis,  was  so  minute  that  it  would 
enter  the  eggs  before  they  were  laid  by  the  moth,  so  that  the 
larvae  were  affected  from  the  time  they  hatched,  although  the 
disease  did  not  manifest  itself  until  a  later  stage  in  their  devel- 
opment. The  disease  is  known  as  pebrine,  and  was  the  first 
disease  proved  to  be  due  to  an  infection  by  a  Protozoan 
parasite.  In  several  countries  where  silk-worm  growing  is 
an  important  industry,  Government  experts  now  examine  all 
the  eggs  that  are  used  for  hatching  and  only  those  that,  by 


PARASITIC  PROTOZOA 


365 


microscopical  examination,  are  shown  to  be  free  from  the  para- 
site are  sent  to  the  growers. 

Epidemics  Among  Fishes. — Sometimes  in  the  United  States, 
and  more  frequently  in  Europe,  destructive  epidemics  appear 
among  the  fishes  in  lakes  or  rivers.  Hundreds  of  thousands 
of  fish  may  die  and  be  washed  upon  the  shores  and  the  particu- 
lar species  attacked  may  be  almost  exterminated  in  some 
regions.  The  diseases  responsible  for  these  epidemics  are 
caused  by  various  species  of  Myxosporida,  which  attack  and 
destroy  the  tissues  of  their  hosts,  often  causing  many  serious 
tumors  over  the  body.  Young  fish  are  especially  apt  to  suffer 
from  the  attacks  of  these  parasites. 


DISEASES  CAUSED  BY  INVISIBLE  MICROORGANISMS 

There  are  a  number  of  diseases  the  causative  agents  of  which 
are  not  yet  definitely  known.     Nevertheless  it  has  been  demon- 


FIG.  155. — Stable-fly,   Stomoxys  calcitrans,   after  engorging    itself 
blood.     (About  three  times  natural  size.) 


with 


strated  that  many  of  these  are  caused  by  living  organisms, 
probably  too  small  to  be  seen  by  any  microscopes  that  have 
yet  been  invented.  More  refined  microscopic  methods  may 
sometime  reveal  some  of  these  to  us,  and  we  may  then  be  able 
to  determine  their  relation  to  other  known  forms. 

That  yellow  fever  is  caused  by  such  an  organism  has  been 
definitely  shown,  and  although  we  do  not  know  the  parasite 


366     ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

we  know  much  of  its  life-history,  and  certain  investigators 
do  not  hesitate  to  express  their  belief  that  it  belongs  to  the 
genus  Spirochceta.  Yellow  fever  is  transmitted  only  by  the 
yellow  fever  mosquito. 

Infantile  paralysis,  or  poliomyelitis,  is  also  caused  by  one 
of  these1  ultra-microscopic  parasites,  which  can  probably  be 
distributed,  as  recently  indicated  by  experiments  with  mon- 
keys, by  the  common  stable-fly,  Stomoxys  calcitrans.  The  dis- 
ease seems  also  to  be  directly  contagious. 

Cattle  plague,  canine  distemper,  swamp  fever  of  horses,  hog 
cholera  and  several  other  diseases  also  belong  to  the  group  pro- 
duced by  invisible  parasites.  Some  of  them  will  probably 
be  found  to  be  caused  by  animal  parasites,  others  by  bacteria. 

1  It  has  recently  been  found  to  be  visible  in  certain  stages,  although 
invisible  in  others. 


CHAPTER  XXIX 
INSECTS  AND  DISEASE 

We  have  already  learned  (Chapter  XXVIII)  that  insects  are 
the  necessary  hosts  of  the  parasites  that  cause  some  of  our  worst 
diseases,  and  that  the  spread  of  these  diseases  depends  wholly 
on  the  presence  of  the  infected  insects.  It  is  only  during  the 
present  century  that  the  very  great  importance  that  insects 
thus  bear  to  our  health  has  been  realized,  and  many  of  the  most 
important  recent  discoveries  in  medical  science  have  had  to  do 
with  this  relation  of  insects  to  some  of  the  common  scourges 
that  afflict  man  or  his  domestic  animals. 

Since  it  was  shown  beyond  all  doubt  that  malarial  fevers 
depend  wholly  on  the  presence  of  infected  mosquitoes  (page 
361),  successful  efforts  have  been  made  to  control  these  insects 
in  some  of  the  places  where  the  disease  was  most  common. 
As  mosquitoes  breed  only  in  quiet  water  the  problem  of 
control  is  not  as  great  as  it  would  at  first  appear  to  be,  and  there 
is  now  no  reason  why  almost  any  community  should  not  rid 
itself  of  these  disease-bearing  pests.  In  temperate  regions 
malaria  is  not  as  fatal  as  it  is  in  the  tropics  where  it  is  the  cause 
of  one-fourth  to  one-half  of  all  the  sickness.  Yet  it  has  been 
estimated  that  the  annual  monetary  loss  due  to  sickness  from 
malaria  in  the  United  States  is  many  millions  of  dollars.  The 
suffering  and  misery,  the  loss  of  vitality  of  young  and  old, 
and  the  death  of  twelve  thousand  persons  each  year,  are  results 
of  malaria  the  importance  of  which  cannot,  of  course,  be 
stated  in  dollars  and  cents. 

Almost  every  day  there  is  an  increase  in  the  evidence  that 
shows  how  dangerous  are  such  common  and  long  tolerated 
household  pests  as  house-flies  and  their  near  relatives,  the  stable- 
flies,  flesh-flies  and  others.  That  these  insects  do  aid  in  the 
dissemination  of  certain  of  our  germ-caused  diseases,  as  typhoid 

367 


368  ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


and  tuberculosis,  is  sure.  That  they  may  aid  in  distributing 
others  is  highly  probable.  Mosquitoes  and  house-flies  will  be 
feared  in  the  not  far  distant  future  as  venomous  snakes  are 
now.  And  they  will  be  fought  even  more  vigorously,  for 
their  abundance  makes  them  immensely  more  dangerous. 

Life  History  and  Habits  of  Mosquitoes. — Mosquitoes  lay 
their  eggs  in  water,  or  in  places  where  water  is  apt  to  accumu- 
late. Some  species  fasten  the  eggs  together  in  little  masses 
that  float  on  the  surface  and  look  like  small  particles  of  soot  at 


\ 


FIG.  156. — Mosquito  eggs  and  larvae,    Theobaldia   incidens;  two  larvae 
feeding  on  bottom,  others  at  surface  to  breathe.     (Enlarged.) 

first  glance.  Other  species  lay  their  eggs  singly,  some  floating 
about  on  the  surface  of  the  water,  others  sinking  to  the  bot- 
tom where  they  remain  until  the  young  issue.  In  the  summer 
time  the  eggs  hatch  in  thirty-six  to  forty-eight  hours.  The 
larvae,  or  "wrigglers,"  are  fitted  only  for  aquatic  life,  but  they 
must  obtain  their  oxygen  directly  from  the  air  and  so  have 
to  come  to  the  surface  to  breathe.  This  is  an  important  thing 
to  remember  when  considering  means  for  their  control.  The 
larvae  of  most  mosquitoes  have,  on  the  eighth  abdominal  seg- 


INSECTS  AND  DISEASE  369 

ment,  a  rather  long  breathing  tube,  the  tip  of  which  is  thrust 
just  above  the  surface  of  the  water  when  they  come  up  to 
breathe.  Other  larvae  do  not  have  such  a  breathing  tube,  the 
spiracles  which  open  into  the  trachea  being  situated  on  the 
surface  of  the  eighth  segment.  The  pupae  of  all  species  are 
active  but  take  no  food. .  The  two  trumpet-shaped  breathing 
tubes  of  the  pupae  are  situated  on  the  thorax,  and  when  the 
pupae  come  to  rest  these  extend  just  above  the  surface  of  the 
water.  When  the  adult  is  ready  to  issue  the  pupal  skin  splits 
along  the  back  and  the  mosquito  slowly  comes  forth,  usually 


FIG.  157. — Mosquito  pupae,  T.  incidens,  resting  at  the  surface  of  the  water. 

(Enlarged.) 

resting  for  a  short  time  on  the  cast-off  pupal  skin  until  the  wings 
become  dry  and  firm  enough  to  use. 

Malaria-carrying  Mosquitoes. — In  the  United  States  only 
mosquitoes  belonging  to  the  genus  Anopheles  carry  malaria,  so 
it  is  important  to  be  able  to  distinguish  the  members  of  this 
genus  in  their  various  stages.  The  eggs  of  Anopheles  are  laid 
singly,  but  are  often  found  together  in  groups  of  three  or  four 
floating  on  the  surface  of  the  water.  Each  egg  is  provided  with 
characteristic  membranous  expansions  on  each  side  near  the 
middle.  These  keep  the  eggs  afloat.  The  larvae  feed  largely 
on  minute  plants  or  other  organisms  at  the  surface  of  the  water, 
and  when  feeding  lie  nearly  horizontally,  with  the  body  touch- 
ing the  surface  at  several  points.  The  absence  of  a  breathing 
tube,  and  this  habit  of  always  lying  with  the  body  parallel  to  the 
24 


370    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

surface  of  the  water  when  feeding  or  at  rest,  readily  distinguish 
these  larvae  from  those  of  any  of  the  non-Anopheline,  or  non- 
malarial,  mosquitoes.  The  pupae  are,  however,  not  so  easy  to 
distinguish.  The  adults  of  Anopheles  have  spotted  wings,  a 
character  which  only  a  few  of  our  other  mosquitoes  have. 
With  most  mosquitoes  the  maxillary  palpi  (see  Fig.  159)  of 
the  male  are  long  and  those  of  the  female  very  short,  but  the 


FIG.   158. — A  female  mosquito,  T,  incidens;  note  the  thread-like  antennae. 
(Three  times  natural  size.) 


Anopheles  mosquitoes  have  the  palpi  long  in  both  sexes,  so 
any  female  mosquito  with  long  maxillary  palpi  is  an  Ano- 
pheles. The  males  of  all  mosquito  species  may  be  readily 
distinguished  from  the  females  by  the  big  feathery  antennas. 
The  antennae  of  the  female  are  provided  with  only  a  few  hairs. 
When  an  Anopheles  mosquito  is  resting  on  the  wall  or  ceiling, 
its  body  is  held  at  an  angle  with  the  surface  on  which  it  is  stand- 
ing, as  shown  in  Fig.  163.  Other  mosquitoes  rest  with  their 


INSECTS  AND  DISEASE  37 1 

bodies  nearly  parallel  to  the  surface  on  which  they  are  standing. 
(Compare  Figs.  162  and  163.) 


FIG.  159. — A  male  mosquito,  T.  incident;  note  the  feathery  antennae 
(Three  times  natural  size.) 


FIG.  160. — Anopheles  larvae,  the  one  to  the  right  feeding.     (Enlarged.) 

Mosquito  Control. — Mosquitoes,  in  all  stages  of  their  devel- 
opment, have  many  natural  enemies,  most  important  of  which 
are  fish  and  various  aquatic  insects  that  feed  on  the  larvae 


372    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


and  pupae.     But  often  the  eggs  are  laid  in  water  where  none  of 
the  natural  enemies  occurs,  and  they  then  breed  undisturbed. 


FIG.  161. — Wing  of  Anopheles  maculipennis.     (Eleven  times  natural  size.) 


FIG.      162. — A       non-malarial  FIG.    163. — A   malarial  mosquito, 

mosquito,     Theobaldia     incident,  Anopheles      maculipennis,       female, 

male      standing   on      the     wall.  standing    on    the     wall.        (About 

(About  twice  natural  size.)  twice  natural  size.) 

Such  places  require  careful  attention  when  fighting  mosquitoes. 
All  water  troughs  and  barrels  or  cisterns  should  be  emptied 


INSECTS  AND  DISEASE  373 

frequently,  or  be  kept  covered  so  that  the  mosquitoes  cannot 
get  to  the  water  in  them.  All  tin  cans,  or  other  scattered 
receptacles  that  might  hold  a  little  water,  should  be  removed  or 
placed  so  that  water  will  not  stand  in  them.  Small  ponds 
should  be  drained  or  kept  covered  with  a  film  of  oil  during  the 
summer  time.  Larger  ponds  are  usually  naturally  stocked 
with  fish,  predaceous  insects  and  other  enemies  of  mosquito 
larvae  and  pupae,  so  that  they  are  not  a  source  of  danger  unless 
the  margins  are  filled  with  rushes  or  other  strong  plant  growth. 
Mosquitoes  will  not  breed  in  running  streams,  but  the  quiet 
pools  along  the  sides  may  afford  excellent  breeding  places, 
particularly  if  they  are  cut  off  from  the  rest  of  the  stream. 
Many  species  breed  abundantly  in  wet  pastures  or  meadows, 
and  others  abound  in  the  brackish  tide  pools  in  the  marshy 
land  along  sea-coasts.  Such  marshes  must  be  drained  or 
dyked  so  the  water  will  not  remain  on  them,  or  all  the  little 
pools  must  be  covered  with  oil  if  such  regions  are  to  be  freed 
from  these  pests. 

Yellow  Fever  and  Mosquitoes. — For  many  years  the  cause 
and  method  of  dissemination  of  yellow  fever  was  a  puzzle  to 
physicians  and  scientists.  The  disease  was  always  regarded 
as  highly  contagious  as  well  as  infectious,  and  every  effort  was 
made  to  isolate  patients  and  to  establish  strict  quarantines  in 
infected  regions.  But  all  such  methods  proved  unsatisfactory. 
Many  people  became  ill  without  ever  having  been  near  a  yellow 
fever  patient,  while  others  worked  in  daily  contact  with  sick 
persons  yet  did  not  take  the  disease. 

During  the  American  occupation  of  Cuba  in  1900  yellow 
fever  became  very  prevalent  there  and  a  board  of  army 
medical  officers,  known  as  the  Yellow  Fever  Commission,  was 
appointed  to  study  the  disease  and  try  to  find  some  means  to 
control  it.  Some  years  previously  a  physician  had  suggested 
that  a  certain  species  of  mosquito,  Stegomyia  fasdala  (calopus), 
which  was  always  found  in  regions  where  the  yellow  fever  oc- 
curred, might  be  concerned  in  the  transmission  of  the  disease. 
The  Yellow  Fever  Commission  early  decided  to  put  this  theory 
to  the  test,  and  before  their  experiments  had  been  finished  it 
was  shown  that  yellow  fever  was  transmitted  by  this  mos- 


374    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

quito  and  in  no  other  way.  Since  that  time  many  other  ex- 
periments have  been  made,  and  it  is  now  definitely  known  how 
this  disease  spreads  through  an  infected  region.  The  virus 
that  causes  the  fever  occurs  in  the  blood  plasma  of  the  human 
host,  but  the  yellow-fever  patient  is  a  source  of  infection  for  the 
mosquito  only  during  the  first  three  or  four  days  after  the  fever 
manifests  itself.  The  virus  must  undergo  an  incubation  period 
of  twelve  to  fourteen  days  in  the  mosquito  before  she  is  capable 
of  transmitting  the  disease.  After  this  incubation  period  the 
mosquito  is  infective  for  the  rest  of  her  life.  The  parasite 


FIG.  164. — Yellow-fever  mosquito,  Stegomyia  fasciata.   (About  eight  times 
natural  size.) 

that  causes  the  disease  has  never  been  seen,  probably  because 
it  is  too  small,  but  it  is  believed  that  it  is  one  of  the  large  group 
of  Sporozoan  parasites. 

One  of  the  members  of  the  Yellow  Fever  Commission  died  of 
yellow  fever  during  the  course  of  the  experiments,  and  another 
member  contracted  the  disease  but  recovered.  The  applica- 
tion of  the  knowledge  gained  by  these  studies  enabled  the 
officers  soon  to  check  the  epidemic  of  yellow  fever  then  existing 
in  Cuba.  A  few  years  later  when  the  disease  appeared  in 
virulent  form  in  New  Orleans  it  was  stamped  out  in  a  re- 
markably short  time  by  waging  a  ceaseless  war  against  the 
mosquitoes.  The  Panama  Canal  Zone  has  long  been  regarded 
as  one  of  the  worst  regions  in  the  world  for  yellow  fever  and 
malaria.  Since  the  United  States  began  work  on  the  Canal 
persistent  efforts  have  been  made  to  control  the  mosquitoes 
there.  These  efforts  have  been  so  successful  that  there  has 
been  no  yellow  fever  in  the  Canal  Zone  for  several  years,  and 
cases  of  malaria  are  comparatively  rare. 


INSECTS  AND  DISEASE  375 

The  yellow-fever  mosquito  is  a  domestic  insect.  It  is  seldom 
found  far  from  human  habitation  and  for  this  reason  can  be 
comparatively  easily  controlled,  for  if  every  possible  breeding 
place  within  a  few  hundred  feet  of  every  house  was  properly 
cared  for  this  mosquito  would  no  longer  be  present. 

Fleas  and  Plague. — Plague  is  a  disease  that  for  ages  was 
regarded  as  one  of  the  greatest  of  human  scourges,  because 
when  once  started  in  a  region  there  seemed  to  be  no  way  to  stop 
its  ravages.  But  it,  too,  has  been  conquered  within  the  last 
decade  by  the  discovery  of  the  cause  of  the  disease,  and  the 
way  -in  which  it  is  transmitted  from  one  host  to  another. 

Plague  is  primarily  a  disease  of  rats  and  other  rodents,  and  it 
is  commonly  spread  by  the  fleas  with*  which  these  animals  are 
always  infested.  When  a  rat  dies  of  the  plague  the  fleas  which 
have  been  sucking  its  blood  leave  it  for  some  other  host.  As 
most  of  the  rat-fleas  will  also  bite  man  the  infected  fleas  may 
communicate  the  disease  to  him. 

The  disease  is  caused  by  the  presence  in  the  blood  of  a 
bacillus,  Bacillus  pestis.  There  are  several  types  of  plague 
distinguished  by  the  way  in  which  they  affect  the  patient,  and 
they  are  probably  spread  in  different  ways.  The  bubonic 
plague  is  the  most  common.  It  may  occur  as  sporadic  cases 
among  animals  and  be  transferred  from  them  to  man  by  fleas. 
Under  favorable  conditions  this  type  may  become  epidemic. 
Pneumonic  and  septicaemic  plague  are  more  virulent  types,  and 
may  be  transmitted  directly  from  man  to  man  and  probably 
also  conveyed  by  insects. 

In  the  efforts  to  control  the  last  outbreak  of  plague  that 
occurred  in  the  United  States  the  whole  fight  was  directed 
against  the  rats  that  had  the  disease  and  against  the  fleas  that 
carried  the  infection  to  man.  Hundreds  of  thousands  of  rats 
were  killed,  their  breeding  places  destroyed,  warehouses  and 
storerooms  made  rat-proof,  covered  garbage  cans  were  required 
in  every  yard,  and  many  other  measures  were  taken  to  make  it 
impossible  for  rats  to  exist  in  any  great  numbers  in  the  infested 
region.  In  this  way  there  was  stamped  out  in  a  remarkably 
short  time  an  epidemic  which  might  at  an  earlier  time  have 
proved  a  national  calamity.  In  some  places  ground-squirrels 


376    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


have  become  infected  with  the  plague,  and  the  Government  is 
now  waging  a  war  against  them  in  order  that  the  disease  may 
not  be  kept  alive  in  them  and  again  become  epidemic  among  rats 
and  man. 

There  are  four  species  of  fleas  occurring  in  the  United  States 
that  are  commonly  found  on  rats.  Two  of  these  are  also 
common  pests  of  man,  and  the  others  do  not  hesitate  to  bite 
man  when  they  have  a  chance,  so  that  all  may  transmit  the 
plague  from  diseased  rats  to  human  beings.  The  cat  and  dog- 


FIG.  165. — Human-flea,  Pulex,  irritans ;  female. 

size.) 


(Twenty  times  natural 


flea,  Ctenocephalus  canis,  is  probably  the  most  common  of  them. 
It  occurs  in  all  places  where  cats  and  dogs  are  kept,  and  is  often 
more  common  in  houses  and  a  worse  pest  than  the  human-flea, 
Pulex  irritans,  which  is  always  a  troublesome  and  persistent 
biter.  The  common  rat-flea  of  the  United  States,  Ceratophyl- 
lusfasciatus,  and  the  Indian  rat-flea,  or  plague-flea,  Xenopsylla 
(Lamopsylla)  cheopus,  are  not  so  troublesome  to  man. 
As  fleas  breed  in  the  dust  under  the  carpets,  in  the  cracks  of 


INSECTS  AND  DISEASE  377 

the  floors,  and  in  the  sleeping  places  of  cats  and  dogs,  all  these 
places  must  be  thoroughly  cleaned  when  a  house  becomes 
infested  with  fleas.  Fleas  are  less  apt  to  be  troublesome  in 
houses  where  rugs  are  used  instead  of  carpets,  as  the  rugs  are 
more  often  taken  outside  for  dusting  and  the  floors  more 
thoroughly  cleaned.  Mats  that  can  be  easily  cleaned  should 
be  provided  for  the  sleeping  places  of  dogs  and  cats,  and  these 
animals  should  of  course  be  kept  out  of  doors.  Benzine, 
naphthaline,  pyrethrum  and  other  substances  are  sometimes 
used  against  fleas,  but  the  results  are  not  wholly  satisfactory. 
It  is  possible  to  kill  all  of  the  insects  in  the  house  by  fumigation, 
but  fumigating  is  dangerous  unless  done  by  an  experienced 
person. 

House-flies. — Until  a  few  years  ago  the  house-fly  was  looked 
on  as  a  harmless,  although  somewhat  troublesome,  household 
pest,  and  was  even  regarded  with  some  favor  as  it  was  sup- 
posed that  it  was  of  service  as  a  scavenger.  But  careful  studies 
of  the  insect  and  its  habits  have  taught  us  to  regard  it  in  quite 
a  different  light,  and  it  is  now  regarded  as  one  of  the  most 
dangerous  insects.  It  is  hard  to  conceive  of  a  better  carrier  of 
small  particles  of  filth  and  germs,  or  one  with  better  opportuni- 
ties for  collecting  and  distributing  them.  Almost  every  part 
of  its  body,  and  almost  all  of  its  habits,  particularly  adapt  it 
for  the  picking  up  and  distribution  of  filth  and  germs.  The 
whole  body  is  provided  with  a  covering  of  spines  and  short  soft 
hair  in  which  particles  of  dirt  are  easily  carried.  The  blunt 
end  of  the  proboscis  by  which  the  fly  sucks  up  its  liquid  food  is 
provided  with  numerous  ridges  and  depressions  so  that  some  of 
the  material  on  which  the  fly  is  feeding  is  carried  from  one  arti- 
cle of  food  to  another.  The  legs  are  particularly  hairy,  and  the 
last  segment  of  each  of  the  feet  is  furnished  writh  two  little 
pads  which  are  covered  with  innumerable  closely-set  hairs  that 
secrete  a  sticky  substance.  It  is  the  presence  of  these  hairs  on 
its  feet  that  enables  the  fly  to  walk  on  smooth  perpendicular 
surfaces,  such  as  the  windowpane,  or  on  the  ceiling,  and,  inci- 
dentally, to  carry  along  samples  of  the  filth  through  which  or 
over  which  it  walks. 

Ninety-eight  per  cent,  of  the  house-flies  lay  their  eggs  in  horse 


378    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

manure,  the  others  breeding  in  cow  manure,  human  excrement 
or  other  filth.     Each  female  lays  from  120  to  150  eggs  at  a 


FIG.  166. — The  house-fly,  Musca  domestica.     (Eight  times  natural  size.) 

time,  and  may  lay  five  or  six  batches  of  these  at  intervals  of  a 
few  days.     These  eggs  hatch  in  ten  to  twenty-four  hours,  and 


INSECTS  AND  DISEASE 


379 


the  whitish  maggots  feed  and  grow  in  the  filth  for  three  or  four 
days  before  changing  to  the  quiescent  pupal  stage  which  lasts 
four  or  five  days  longer.  Then  the  adult  fly  issues.  Some  of 
the  filth  through  which  the  fly  has  to  crawl  as  it  issues  from  the 
pupa  inevitably  clings  to  the  little  brush-like  feet  and  the  hairy 
body.  If  the  flies  bred  only  in  stable  manure  and  flew  directly 
from  the  stable  to  the  house  there  would  be  comparatively 


FIG.  167.— Head  of  house-fly,  showing  eyes,  antennae  and  mouth-parts. 
(Much  enlarged.) 

little  reason  to  complain,  at  least  from  a  sanitary  standpoint, 
for  the  amount  of  filth  they  carry  from  the  barnyard  to  our  food 
would  be  of  little  consequence.  Too  often,  however,  they  visit 
other  places  before  calling  on  us,  and,  unfortunately,  these  other 
places  are  often  most  unclean.  Experiments  have  shown 
that  when  the  fly  walks  over  germ-infected  material  many  of 


380    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  germs  are  carried  and  distributed  to  other  substances  over 
which  it  may  walk,  and  that  bacteria  may  live  in  the  alimentary 
canal  of  the  fly  and  even  increase  in  numbers  there  and  remain 
virulent  in  the  excreta,  or  "fly  specks,"  for  as  long  as  twenty 
days  after  these  specks  have  been  deposited.  It  has  been 
shown  also  that  larvae  of  flies  may  feed  on  bacteria  and  the 
same  organisms  be  recovered  from  the  adult  flies  which  develop 


FIG.   1 68. — Foot   of   house-fly,   showing   claws,   hairs,   pulvilli   and 
minute  clinging  hairs  on  the  pulvillas.     (Greatly  enlarged.) 


the 


from  the  larvae.  All  this  indicates  some  of  the  possible  ways  in 
which  flies  may  carry  filth  or  disease  germs  from  their  dangerous 
breeding  or  feeding  grounds  directly  to  foods  which  may  be 
exposed  in  the  market  place,  dairy,  or  home. 

It  has  been  proved  beyond  a  doubt  that  flies  play  an  impor- 
tant part  in  the  dissemination  of  typhoid  germs,  and  it  has 
also  been  shown  that  they  carry  some  of  the  germs  that  cause 
the  sickness  and  death  of  many  babies,  especially  bottle-fed 
babies.  Time  and  again  it  has  been  noted  that  outbreaks  of 


INSECTS  AND  DISEASE 


381 


enteritis  and  other  intestinal  diseases  occur  during  fly  time,  and 
a  moment's  thought,  in  the  light  of  our  knowledge  of  the  habits 
of  flies,  will  show  how  easy  it  is  for  the  milk  to  become  infected 
around  dairy  barns  or  milk  wagons  where  the  flies  are  always 
found  in  great  numbers.  It  is  quite  possible,  too,  that  flies 
may  sometimes  be  concerned  in  the  transmission  of  the  germs 


FIG.  169. — Larvae  and  pupse  of  house-fly,  Musca  domestica,  in  manure. 
(Natural  size.) 

that  cause  tuberculosis,  influenza  and  other  dreaded  diseases. 
Of  course  only  a  small  proportion  of  the  flies  carry  disease 
germs,  but  they  are  all  filthy,  and  it  is  impossible,  without 
careful  laboratory  analysis,  to  distinguish  those  which  carry 
disease  from  those  which  are  merely  dirty. 

The  only  safe  thing  to  do  is  to  banish  them  all,  not  only  from 
the  house  and  the  market  place,  but  from  the  storerooms  and 
dairies  and  all  other  places  where  food  of  any  kind  may  be 


382    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

exposed.  Screens,  sticky  fly  paper,  fly  poisons  and  fly  traps 
about  the  house  will  give  some  relief,  but  there  is  little  use  in 
protecting  the  food  after  it  has  entered  our  homes  if  in  the 
stores  or  markets  or  dairies  it  has  already  been  exposed  to  con- 
tamination by  thousands  of  flies  that  have  visited  it  there. 
The  problem  is  a  larger  one  than  simply  keeping  the  flies  out  of 
our  houses;  larger  but  not  more  difficult,  for  the  remedy  is  sim- 
ple, effective  and  inexpensive.  If  the  manure  in  which  the 
flies  breed  is  hauled  from  the  barn  at  least  once  a  week  and  scat- 
tered thinly  over  a  field,  it  will  dry  so  quickly  that  the  flies  will 
not  breed  in  it.  If  it  is  impracticable  to  scatter  the  manure  at 
once,  it  should  be  composted  at  least  half  a  mile  from  any  dwell- 
ing. Most  livery  stables  have  the  manure  removed  daily, 
but  few  of  them  are  careful  to  see  that  the  bins  or  other  places 
where  the  manure  is  stacked  before  being  hauled  are  thor- 
oughly clean.  Thus  there  is  left  in  cracks  or  corners  enough 
manure  to  serve  as  breeding  places  for  hundreds  of  thousands  of 
flies.  Then,  too,  few  stablemen  take  the  care  to  clean  the  stalls 
as  thoroughly  as  they  should,  and  many  a  one  is  surprised 
when  he  finds  that  the  flies  are  breeding  abundantly  in  the  stalls 
which  he  considered  sufficiently  cleaned.  Finally,  after  every 
effort  has  been  made  to  clean  up  the  breeding  places  of  flies, 
our  attention  should  be  turned  to  trapping  or  poisoning  the  few 
flies  that  may  still  appear.  Many  more  or  less  efficient  fly 
traps  are  on  the  market,  some  of  which,  if  properly  baited, 
do  really  good  work.  Fly  papers  are  often  quite  effective,  but 
they  are  disgusting  unless  kept  out  of  sight.  A  poison  made  by 
adding  one  tablespoonful  of  formaldehyde  to  one-half  a  pint 
of  milk  and  water  forms  a  very  attractive  bait  and  a  deadly 
poison  for  the  flies.  The  best  way  to  use  it  is  to  place  a  piece 
of  bread  in  a  saucer  and  almost  cover  it  with  the  poison, 
milk  and  water. 

The  Stable-fly,  or  Biting  House-fly. — This  is  another  fly 
that  is  commonly  found  in  houses.  It  looks  very  much  like  the 
common  house-fly,  and  only  a  close  observer  will  notice  the 
difference  between  the  two.  The  most  noticeable  and  impor- 
tant difference  is  in  the  character  of  the  mouth  parts.  The  tip 
of  the  proboscis  of  the  house-fly  is  blunt  and  roughened,  fitted 


INSECTS  AND  DISEASE 


383 


for  rasping  and  reducing  to  a  liquid  or  semiliquid  condition 
the  material  upon  which  it  feeds.  The  mouth  parts  of  the 
stable-fly,  on  the  contrary,  form  a  strong  piercing  beak  which 
can  cut  through  even  the  toughest  skin  in  order  that  the  fly 
may  suck  the  blood  of  its  victim.  Persons  are  often  bitten  by 
flies  that  they  believe  to  be  house-flies.  But  house-flies  cannot 
bite,  and  it  will  usually  be  found  that  the  culprits  are  stable- 


FIG.  170. — Stable-fly,  Stomoxys  calcitrans.  Resembles  house-fly  in 
general  appearance,  but  has  pointed,  piercing  and  sucking  beak,  and  the 
vein  which  terminates  near  the  tip  of  the  wing  is  not  so  sharply  angulated 
as  in  the  house-fly.  (See  Fig.  166.)  (Five  times  natural  size.) 

flies.  If  the  wings  of  a  house-fly  and  a  stable-fly  be  carefully 
compared  it  will  be  seen  that  the  fifth  vein  (counting  from  the 
front  margin)  of  the  house-fly's  wing  is  bent  forward  at  a  con- 
siderable angle  while  the  corresponding  vein  in  the  wing  of 
the  stable-fly  is  only  slightly  curved.  The  fourth  and  fifth 
veins  are  the  two  veins  that  end  near  the  tip  of  the  wing.  In 
the  house-fly  the  tips  of  these  veins  are  very  close  together;  in 
the  stable-fly  they  are  rather  widely  separated. 


384    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  stable-flies  develop  in  much  the  same  way,  and  under  the 
same  conditions  as  the  house-flies,  but  they  are  more  apt  to  be 
found  in  cow  manure  or  old  straw  or  other  decaying  vegeta- 
tion, than  in  horse  manure.  The  stable-fly  also  takes  longer 
to  complete  its  development  than  does  the  house-fly,  often 
requiring  three  or  four  weeks  to  pass  through  the  larval  and 
pupal  stages. 

Stable-flies  are  among  the  most  serious  pests  of  cattle  and 
horses,  biting  them  severely  and  causing  considerable  swellings 
in  the  places  where  they  bite.  They  have  recently  been  the 
subject  of  particular  study  and  investigation  because  they  have 
been  suspected  of  being  intimately  connected  with  the  dis- 
tribution of  that  mysterious  disease  known  as  poliomyelitis, 
or  infantile  paralysis.  This  disease,  which  has  been  slowly 
spreading  over  America  as  well  as  most  European  countries,  has 
baffled  the  skill  of  physicians  because  they  have  been  unable 
to  determine  how  it  is  transmitted.  Experiments  have  been 
made  which  show  that  stable-flies  are  capable  of  transmitting 
the  disease  if  they  are  allowed  to  bite  first  an  infected  and  then  a 
healthy  monkey.  While  this  by  no  means  proves  that  it 
really  spreads  the  disease  among  human  beings,  it  yet  adds 
greatly  to  the  evidence  against  this  insect,  so  that  the  flies 
should  be  destroyed  whenever  possible.  The  same  measures 
that  are  necessary  for  the  control  of  the  house-fly  would  aid 
materially  in  controlling  this  insect  also. 

Other  Diseases  Carried  by  Insects. — There  are  many  other 
diseases  that  are  known  to  be  transmitted  by  insects.  Sleep- 


FIG.  171. — Filaria  in  the  thorax,  head  and  labium  of  a  mosquito.     (After 
Castellan!  and  Chalmers.) 

ing  sickness  and  other  diseases  caused  by  trypanosomes  and 
carried  by  tsetse-flies  have  been  discussed  in  Chapter  XXVIII, 
and  in  Chapter  XII  it  has  been  shown  how  mosquitoes  carry 


INSECTS  AND  DISEASE  385 

the  filaria  that  cause  elephantiasis.  Mosquitoes  are  also  prob- 
ably responsible  for  the  spread  of  dengue  or  break-bone  fever. 
We  do  not  yet  know  the  organism  that  causes  the  disease,  but 
experiments  have  shown  that  it  can  be  spread  by  Culexfatigans, 
and  possibly  by  other  species  of  mosquitoes. 

For  a  long  time  the  theory  that  pellagra  is  in  some  way  asso- 
ciated with  the  eating  of  maize  has  been  generally  accepted. 
Recently  Dr.  Sambon  has  suggested  that  pellagra  may  be 
caused  by  some  organism  that  is  transmitted  by  certain  small 
black  flies  belonging  to  the  family  Simulida.  This  theory  is 
not  yet  firmly  established  and  there  are  many  who  do  not 
accept  it  at  all.  The  investigations  that  are  now  being  carried 
on  will  doubtless  soon  settle  the  question.  The  black-flies  are 
very  serious  pests  of  live  stock  and  their  habits  are  discussed 
in  Chapter  XXX.  The  stable-fly  has  also  been  considered 
as  a  possible  agent  in  the  transmission  of  pellegra. 

Certain  little  moth-like  flies,  Phlebotomus  pappataci,  which 
on  account  of  their  habits  are  sometimes  called  "sand-flies," 
carry  an  unknown  germ  that  causes  a  very  infectious  disease 
known  as  three-day  fever,  or  sand-fly  fever.  But  as  this  and 
several  other  diseases  of  lesser  importance  spread  by  insects,  do 
not  occur  in  our  country  we  need  not  discuss  them. 

The  relation  of  ticks  to  several  important  diseases  has  already 
been  discussed  in  Chapters  XIX  and  XXVIII. 


CHAPTER  XXX 


OTHER  INSECTS  AFFECTING  MAN  AND  DOMESTIC 
ANIMALS 

Besides  the  mosquitoes,  house-flies  and  fleas,  there  are 
several  other  insects  that  affect  man  and  his  domestic  animals 
more  or  less  seriously.  The  habits  of  some  of  these  make  it 
quite  possible  for  them  to  carry  infection  from  one  host  to 
another  under  favorable  conditions.  So  aside  from  the  annoy- 
ance and  suffering  they  may 
cause  they  must  always  be  re- 
garded as  potential  sources  of 
greater  danger. 

Flies. — Among  such  trouble- 
some   and    dangerous    insects 


•  FIG.  172. — A  black-fly, 
Simulium  sp.  (About  6 
times  natural  size.) 


FIG.  173. — Horse-fly,  Tabanns 
punctifer.  (A  little  larger  than 
natural  size.) 


various  kinds  of  flies  are  perhaps  most  important.  The  little 
"punkies, "  or  "  no-see- urns,"  Ceratopogon  spp.,  that  often 
occur  in  great  swarms  in  certain  regions,  bite  very  severely  and 
are  extremely  annoying  to  man  and  beast.  The  black-flies,  or 
buffalo-gnats,  Simulium  spp.,  also  fly  in  great  swarms  and 
inflict  very  painful  bites.  The  lancet-shaped  stylets  of  the 

386 


INSECTS  AFFECTING  MAN  AND  ANIMALS    387 

mouth-parts  make  a  wound  into  which  is  injected  poison  from 
the  salivary  glands.  Animals  are  driven  frantic  by  the 
attacks  of  these  pests  and  may  even  suffer  death  unless  they  are 
afforded  some  protection.  Considerable  losses  are  occasioned 
each  year  because  of  farmers  not  being  able  to  work  animals 
in  the  fields  during  the  season  that  these  insects  are  flying. 
The  possible  relation  of  these  flies  to  pellagra  has  been  referred 
to  in  the  preceding  chapter. 

The  larvae  of  the  black-flies  are  aquatic,  attaching  themselves 
to  the  surface  of  rocks  in  swiftly  moving  streams.  It  is 
difficult  to  fight  them  there,  but  some  small  streams  may  be 
cleared  of  their  breeding  places,  or  the  water  may  be  treated 


FIG.  174. — Screw-worm  fly,  Chrysomyia  macellaria.     (Three  times  natural 

size.) 

with  phinotis  oil  and  many  of  the  larvae  destroyed  without 
injuring  the  fish  in  the  stream.  Dense  smudges  will  keep  the 
adults  away,  and  some  protection  may  be  afforded  animals  by 
smearing  them  with  cotton-seed  oil  or  oil  and  tar. 

The  horse-flies,  gad-flies,  breeze-flies  and  deer-flies,  all  be- 
longing to  the  family  Tabanidce,  can  pierce  through  the  toughest 
skin  and  are  often  a  source  of  great  annoyance  to  live  stock. 
Some  of  them  often  attack  man  also.  Cattle  and  horses 
sprayed  with  some  crude  oil  emulsion  are  not  attacked  as 
freely  as  unsprayed  animals.  Laurel  oil  has  recently  been 
recommended  as  a  fly  repellent. 

Horn-flies,  Hamatobia  serrata,  and  the  stable-fly,  Stomoxys 
calcitrans,  are  among  the  most  serious  pests  of  cattle.  Means 
for  controlling  the  latter  have  been  suggested  in  the  previous 


388    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

chapter,  but  it  is  harder  to  control  the  horn-fly  because  it 
breeds  in  the  cow  manure  all  over  the  pasture.  Various 
repellent  washes  are  recommended  for  use,  but  none  is  wholly 
satisfactory. 

The  screw-worm  flies,  Chrysomyia  macellaria,  often  cause 
great  suffering  on  account  of  the  habits  of  the  larvae.  These 
gray-flies,  as  they  are  sometimes  called,  may  lay  a  mass  of  three 
or  four  hundred  eggs  on  the  surface  of  wounds  on  cattle, 
horses,  etc.  The  larvae  which  hatch  from  these  eggs  in  a  few 
hours  make  their  way  into  the  wound  and  feed  on  the  surround- 
ing tissue.  Slight  scratches  that  might  otherwise  quickly  heal 


FIG.  175. — Blow-fly,    Calliphora    vomitoria.     (Two    and    one-half    times 

natural  size.) 

often  become  serious  sores  on  account  of  the  presence  of  these 
larvae.  Many  cases  are  on  record  of  these  flies  laying  their 
eggs  in  the  ears  or  nose  of  children  or  of  persons  sleeping  out  of 
doors  during  the  day.  The  larvae,  burrowing  in  the  mucous 
membrane,  cause  terrible  suffering  and  often  death. 

The  blow-flies,  Calliphora  vomitoria,  the  blue-bottle  flies, 
Lucilia  spp.,  and  the  flesh-flies,  Sarcophaga  spp.,  all  have 
habits  somewhat  like  those  of  the  screw-worm  flies.  The 
flesh-fly,  instead  of  laying  eggs,  deposits  living  larvae  upon 
meat  wherever  it  is  accessible,  and  as  these  larvae  grow  with 


INSECTS  AFFECTING  MAN  AND  ANIMALS    389 

astonishing  rapidity  they  are  able  to  consume  large  quantities 
of  flesh  in  a  remarkably  short  time.  In  this  way  they  may  be 
of  some  importance  as  scavengers. 

The  bot-flies,  family  Oestrida,  are  another  group  of  flies  that 
are  a  great  source  of  annoyance,  and  often  loss,  to  the  stock- 
man. Rarely,  too,  the  larvae  of  some  of  them  may  infest  man. 
The  adult  flies  look  much  like  small  hairy  bumble-bees.  The 
mouth- parts  are  rudimentary  so  they  cannot  bite,  yet  many 
animals  have  an  instinctive  fear  of  them  and  will  do  every- 
thing that  they  can  to  get  away  from  the  pests.  The  common 
bot-fly  of  the  horse,  Gastrophilus  equi,  attaches  its  eggs  to  the 


FIG.  176. — Horse  bot-fly,  Gastrophilus  equi.     (Two  and  one-half  times 
natural  size.) 

hair  of  the  legs  or  some  other  part  of  the  body  of  the  animal. 
The  horse  licks  off  the  eggs  into  its  mouth.  The  eggs  hatch 
just  before  or  after  they  are  licked  off  and  the  larvae  develop 
in  the  alimentary  canal  of  their  host.  Sometimes  the  walls  of  the 
stomach  may  be  almost  covered  with  the  larvae  that  have  at- 
tached themselves  there.  This  of  course  seriously  interferes 
with  the  function  of  this  organ.  When  full  grown,  the  larvae 
pass  from  the  horse  with  the  droppings,  and  complete  their 
transformations  in  the  ground.  There  are  two  other  species  of 
bot-flies  attacking  the  horses.  These  have  habits  similar,  in 
most  respects,  to  the  species  just  described. 


3QO    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

It  is  believed  that  the  bot-flies  of  cattle,  or  the  ox-warbles, 
Hypoderma  lineata,  and  //.  bows,  gain  an  entrance  into  the  ali- 
mentary canal  in  the  same  way,  that  is  by  being  licked  from  the 


FIG.  177. — Bots,   larvae   of  Gastrophilus  equi,   in   stomach   of  horse. 

(Enlarged.) 
i 

hairs  on  the  body  where  the  eggs  have  been  laid  by  the  adult 
•fly.     But  instead  of  passing  on  into  the  stomach  they  penetrate 


FIG.  178. — Ox  warble-fly,  Hypoderma  lineata.     (About  two  and  one-half 
times  natural  size.) 

the  Walls  of  the  esophagus  and  later  make  their  way  through  the 
tissues  of  the  body,  until  at  last  they  reach  a  place  along  the 
back  just  under  the  skin.  Here,  while  completing  their 


INSECTS  AFFECTING  MAN  AND  ANIMALS   391 

development,  they  make  more  or  less  serious  sores.  When  fully 
mature  their  larvae  drop  to  the  ground  and  undergo  their  trans- 
formation to  pupae  and  finally  to  flies.  Some  entomologists 
believe,  however,  that  the  eggs  are  laid  on  the  backs  of  the 
cattle  and  that  the  larvae  bore  through  the  skin  to  the  place  where 
they  are  to  complete  their  larval  development.  Although  this  is 
one  of  the  most  common  pests  of  cattle  this  question  in  regard 
to  its  life-history  has  never  been  definitely  settled.  The  sheep 
bot-flies,  Oestrus  ovis,  lay  their  eggs  in  the  nostrils  of  sheep. 
The  larvae  pass  up  into  the  frontal  sinuses,  where  they  feed  on 
the  mucus  and  tissues,  causing  great  suffering  and  loss.  Many 


FIG.  1 79. — Bot,  larva  of  Hypoderma  lineata,  from  cow.   j  (Enlarged.) 

other  species  of  animals  are  infested  by  their  own  particular 
species  of  bots.  Several  instances  are  recorded  where  the  ox-, 
warbles  have  occurred  in  man,  always  causing  much  suffering 
and  sometimes  death. 

Horses  and  cattle  that  can  rest  in  the  shade  during  the  hot- 
test part  of  the  day  are  not  bothered  as  much  by  bot-flies  as 
are  animals  that  do  not  have  such  protection.  Cattle  often 
obtain  further  protection  by  standing  in  the  water  when  it  is 
available.  Horses  that  are  thoroughly  groomed  and  kept 
free  from  the  eggs  of  the  bot-flies  will  not,  of  course,  be  infested 
with  the  larvae.  After  they  have  gained  an  entrance  little 
can  be  done  to  cause  the  larvae  to  leave  the  alimentary  canal 
of  the  host  until  they  are  fully  developed.  The  ox-warbles 


392    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

are  much  more  serious  pests,  but  fortunately  they  can  be 
controlled  by  concerted  action  on  the  part  of  all  of  the  stock 
owners  in  a  community.  After  the  larvae  have  attained  con- 
siderable size  they  are  easily  detected  as  they  lie  under  the 
skin  on  the  backs  of  the  cattle.  When  they  are  nearly  ready 
to  issue  they  can  easily  be  squeezed  out  and  destroyed.  They 


FIG.  180. — Body-louse,    Pediculus    vestimenti.     (About     eighteen     times 
natural  size.) 

may  also  be  killed  while  still  under  the  skin,  but  bad  sores  are 
apt  to  result  if  this  is  done  so  it  is  much  better  to  squeeze  them 
out.  If  all  of  the  cattle  owners  in  a  community  attend  to  this 
early  each  spring,  it  is  evident  that  the  number  of  bot-flies 
will  soon  be  so  reduced  that  they  will  cause  little  trouble. 

Lice. — There  are  two  distinct  groups  of  wingless  parasitic 
insects  commonly  called  lice.  One  group,  the  blood-sucking 
lice,  belongs  to  the  family  Pediculidce,  order  Hemiptera;  the 
other,  the  biting  lice,  constitutes  an  independent  small  order,  the 


INSECTS  AFFECTING  MAN  AND  ANIMALS    393 

Mallophaga.  The  Pediculidce  are  confined  to  mammals,  the 
three  species  found  on  man  and  a  few  that  infest  domestic  ani- 
mals being  the  best  known.  The  mouth  parts  are  fused  to  form 
a  flexible  sucking  tube,  and  the  feet  are  provided  with  a  single 
strong  curved  claw  which  enables  them  to  cling  to  the  hair  of 
their  host.  The  head-louse,  Pediculus  capitis,  is  very  annoying 
on  account  of  the  intense  itching  caused  by  the  bite.  The 
eggs,  called  "nits,"  are  attached  to  hairs,  and  are  very  hard 


FIG.  181. — The  sucking  louse  of  the  horse,  Hamate pinus  asini.     (About 
twenty  times  natural  size.) 

to  remove.  These  lice  are  never  common  where  clean- 
liness is  the  rule,  but  under  certain  conditions  they  may 
be  met  with.  Thorough  combing  and  washing  followed 
by  an  application  of  pomade,  vaseline  or  some  such  greasy 
substance  wTill  get  rid  of  the  pest.  The  body  lice,  P. 
•vestimenti,  known  as  "graybacks,"  "crumbs,"  "seam-squir- 
rels," live  on  the  body  and  hide  among  the  clothing. 
They  sometimes  become  very  serious  pests  where  the 
surroundings  are  not  sanitary,  but  can  be  controlled  by 


394    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

cleanliness.  Infested  clothes  that  may  contain  some  of  the 
eggs  should  be  boiled  or  steamed,  or  the  inside  of  the  seams 
smeared  with  mercurial  ointment.  The  crab-louse,  Pthirius 
inguinalis,  lives  on  the  hairs  on  protected  parts  of  the  body. 
Sulphur  and  mercurial  ointment  are  ths  remedies  used. 


FIG.  182. — A  chicken-louse,  Menopon  pallidum.     (Greatly  enlarged.) 

Most  of  the  sucking  lice  on  domestic  animals  belong  to  the 
genus  Hcematopinus.  Dogs,  horses,  cattle,  sheep,  hogs  and 
other  animals  are  infested  with  species  peculiar  to  themselves. 
The  animals  may  be  freed  from  these  pests  by  washing 


INSECTS  AFFECTING  MAN  AND  ANIMALS   395 

thoroughly  with  tobacco  water,  or  dilute  carbolic  acid,  or  dilute 
kerosene  emulsion.  Ointments  made  of  kerosene  and  lard, 
or  sulphur  one  part  and  lard  four  parts,  are  effective.  It  is 
possible  to  fumigate  an  animal  by  inclosing  all  but  the  head  in 
a  sack  or  tent  and  burning  sulphur  or  tobacco  inside  the  tent. 

The  Mallophaga  do  not  suck  blood,  but  feed  on  bits  of  dry 
feathers  or  hair  which  they  bite  off  with  their  small  sharp  jaws. 
They  are  commonly  called  bird-lice,  because  most  of  them 
infest  birds,  but  some  species  are  found  on  mammals  where 
they  feed  on  the  hair  or  epidermal  scales.  The  injury  done  to 
the  host  is  due  chiefly  to  the  irritation  caused  by  the  insects 
wandering  over  the  body.  They  sometimes  occur  in  such 
numbers  as  seriously  to  affect  barnyard  fowls.  The  common 
chicken-louse,  Menopon  pallidum,  is  about  one- twentieth  of 
'an  inch  long  and  is  an  unusually  swift  and  active  little  pest. 
The  affected  fowls  make  an  effort  to  rid  themselves  of  the  pest 
by  bathing  in  fine  dust.  Good  dust  baths  should  always  be 
available  for  this  purpose,  and  the  roosts  should  be  kept  clean. 
Badly  infected  poultry  houses  should  be  sprayed  with  kerosene 
or  fumigated  by  burning  sulphur  in  them,  and  then  thoroughly 
whitewashed.  • 

Dogs,  horses  or  other  domestic  animals  infected  with  biting 
lice  may  be  treated  as  recommended  for  sucking  lice. 

Bedbugs — Although  bedbugs,  Acanthia  lectularia,  usually 
occur  only  in  neglected  houses,  they  may  be  accidentally  in- 
troduced into  the  cleanest  places,  and  they  are  often  met  with 
in  hotels.  They  cannot  fly,  as  they  have  no  wings,  but  they  are 
active  crawlers  and  may  migrate  from  house  to  house  when  food 
becomes  scarce.  They  are  more  commonly  distributed  on 
clothing,  especially  bed  clothing  and  upholstered  furniture. 
When  crushed  they  give  off  a  very  disagreeable  odor  which  is 
due  to  the  secretions  from  glands  at  the  base  of  the  abdomen. 
They  are  nocturnal  in  their  habits,  hiding  away  in  cracks  in 
bedsteads  or  other  furniture  or  in  the  walls  during  the  day. 
Their  very  flat  soft  bodies  are  capable  of  being  squeezed  into 
seemingly  impossible  places.  The  mouth-parts  are  fitted  for 
piercing  and  sucking  blood.  Normally  they  feed  only  on  blood,, 


396    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

but  they  may  possibly  subsist  for  a  time  on  moisture  in  wood 
or  dust. 

The  bite  is  very  irritating  to  most  people,  but  no  poison  is 
secreted.  The  recurrent  fever  of  Europe  isprobably  transmitted 
by  bedbugs,  and  it  is  quite  possible  that  other  diseases  also 
may  be  carried  by  this  unclean  pest.  Recent  experiments  have 
indicated  that  it  may  prove  to  be  one  of  the  agents  in  the 
spread  of  the  bacillus  that  causes  leprosy. 


FIG.  183. — Bedbug,  Acanthia  lectularia.     (About  six  times  natural  size.) 


The  simplest  way  to  get  rid  of  bedbugs  is  to  clean  all  the 
furniture  and  woodwork  thoroughly.  Carpets  and  rugs  should 
be  removed,  and  every  crack  and  crevice  in  furniture,  picture 
frames,  walls  and  floors  should  be  given  a  liberal  treatment 
with  gasoline.  Corrosive  sublimate  (bichloride  of  mercury) 
in  water  or  alcohol  may  be  used  for  the  same  purpose,  but  it  is 
more  expensive  than  gasoline  and  more  apt  to  injure  some 
articles.  As  the  water  or  alcohol  evaporates  a  thin  coating  of 
the  powder  is  left  that  gives  a  large  measure  of  protection  as 
long  as  it  lasts.  Fumigation  with  hydrocyanic  gas  is  more  satis- 
factory, but  this  gas  should  be  used  only  by  some  experienced 


INSECTS  AFFECTING  MAN  AND  ANIMALS    397 


person  who  is  well  aware  of  the   danger  attending  its  use. 

Bedbugs  are  sometimes  found  in  poultry  houses  where  they 
may  be  very  annoying.  The  closely  related  bugs  often  found 
so  abundantly  in  swallows'  nests  and  in  other  places  out  of 
doors  do  not  become  household  pests. 

Cockroaches. — Like  the  bedbugs,  the  cockroaches  are  night 
foragers.  But  they  are  much  less  particular  about  the  kind  of 
food  that  they  eat.  Their  mouth-parts  are  fitted  for  biting. 
Kitchens,  pantries,  restaurants,  hotels  and  bakeshops  where  the 
air  is  warm  and  humid,  are  their  favorite  haunts,  and  almost 
any  kind  of  organic  matter  that  can 
be  found  around  such  places  suits 
their  taste. 

There  are  four  common  species 
found  in  dwellings  in  this  country, 
only  one  of  which  is  native.  The 
American  roach,  Periplaneta  americana, 
is  the  largest  of  these.  It  is  light 
brown  in  color  and  about  one  and  one- 
half  inches  long.  The  Australian 
roach,  P.  australasia,  is  nearly  as  large 
as  the  preceding  species,  but  is  darker 
in  color.  The  Asiatic  roach,  P.  orien- 
talis,  or  black  beetle,  as  it  is  some- 
times called,  is  about  one  inch  long, 
and  brownish  black  in  color.  The 
wings  of  the  female  are  rudimentary, 

and  in  the  male  the  wings  do  not  reach  to  the  tip  of  the 
abdomen.  The  most  abundant  and  destructive  of  the  group 
in  many  parts  of  the  United  States  is  the  little,  yellowish- 
brown,  German  cockroach,  Ectobia  germanica,  which  is  only 
about  half  an  inch  long.  It  is  often  caUed  croton-bug  because 
of  its  intimate  association  with  the  pipes  of  New  York  City's 
Croton  water  system. 

The  eggs  of  cockroaches  are  laid  in  small,  purse-like,  horny, 
brown  cases  which  are  usually  carried  about  by  the  female 
until  the  young  are  ready  to  issue.  It  probably  takes  about  a 
year  for  the  young  to  become  fully  developed. 


FIG.  184. — The  croton- 
bug,  or  German  cock- 
roach, Ectobia  germanica. 
(Twice  natural  size.) 


398    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Although  the  actual  damage  done  by  these  insects  is  not 
often  very  great,  they  are,  on  account  of  their  unpleasant  odor 
and  their  habit  of  crawling  into  everything,  most  disgusting 
creatures  to  have  about  the  house.  It  is  suspected  that  they 
may  be  concerned  in  the  transmission  of  certain  diseases  by 
contaminating  food.  Fumigation  with  hydrocyanic  gas  is 
the  best  remedy  to  use  when  this  is  practicable.  There  are 
many  roach  powders  on  the  market,  but  few  of  them  are 
wholly  satisfactory.  Indeed  it  is  usually  only  by  a  combina- 
tion of  several  methods  of  fighting,  such  as  poisoning,  trap- 
ping and  sealing  up  their  hiding  places,  that  one  can  hope  to 
control  the  roaches  in  a  badly  infested  house,  unless  fumiga- 
tion is  resorted  to.  All  the  cracks  and  crevices  where  the 
roaches  hide  should  be  filled  if  possible;  when  this  cannot  be 
done  such  places  should  be  thoroughly  syringed  with  a  solution 
of  bichloride  of  mercury.  Sweet  chocolate  or  sugar  and  pow- 
dered borax  thoroughly  ground  together  make  a  very  good 
poison.  It  is  most  readily  eaten  from  pieces  of  slightly 
moistened  bread.  Phosphorous  paste  makes  a  good  poison 
when  spread  on  moist  bread.  Many  roaches  may  be  trapped 
by  placing  food  or  some  other  attractive  article  in  the  bot- 
tom of  a  deep  vessel  and  arranging  sticks  or  papers  so  the  in- 
sects can  easily  crawl  from  the  floor  to  the  edge  of  the  vessel. 
The  sides  of  the  vessel  should  be  steep  enough  so  the  roaches 
cannot  crawl  out  after  they  have  entered  it. 

Ants. — In  the  southern  states  a  few  of  the  common  ants 
may  become  of  some  importance  in  the  field  or  garden  on  ac- 
count of  their  habit  of  making  large  bare  areas  around  their 
nests  or  because  they  strip  the  foliage  from  plants.  The 
introduced  Argentine  ants,  Iridomyrmex  humilis,  are  the 
worst  of  these,  as  they  do  considerable  damage  to  citrus  and 
other  trees  by  destroying  the  opening  blossoms  or  the  very 
young  fruit.  In  badly  infested  regions  almost  all  kinds  of 
flowers  are  attacked.  All  kinds  of  stored  food  products  may 
be  infested  by  these  ants  and  the  loss  in  store  rooms  from  this 
source  is  often  important.  But  it  is  as  household  pests  that 
ants  are  of  primary  interest.  One  little  red  species,  Mono- 
morium  pharaonis,  makes  its  home  in  houses,  building  nests 


INSECTS  AFFECTING  MAN  AND  ANIMALS    399 

between  the  walls,  under  the  hearthstones,  or  in  other  suitable 
places.  The  small  black  ant,  M.  minimum,  the  pavement-ant, 
Tetramorium  ccespitum,  of  many  eastern  cities,  and  other 
species  which  have  their  nests  out  of  doors,  frequently  invade 
houses  and  cause  great  annoyance  by  getting  into  all  kinds 
of  food.  As  in  the  field  so  in  the  houses  the  Argentine  ant  is 
by  far  the  most  important  in  regions  where  it  occurs.  Indeed 
in  places  where  this  introduced  species  is  well  established  the 
other  species  disappear,  for  the  intruder  attacks  and  finally 
overcomes,  by  sheer  force  of  numbers,  all  other  kinds  of  ants. 

Nearly  all  ants  live  in  large  colonies  in  a  common  nest,  but 
the  Argentine  ants  build  small  nests  or  burrows  anywhere 
throughout  the  infested  region.  Not  only  are  the  Argentine 
ants  more  numerous  than  other 
species,  but  they  are  more  per- 
sistent in  their  search  for  food, 
and  methods  that  usually  afford 
protection  from  other  ants  are 
of  little  or  no  avail  against 
this  introduced  marauder. 

The  best  way  to  get  rid  of  FIG.  185. — Argentine  ant,  In- 
most  ants  is  to  find  the  nest  and  fjjjjj^  humilis-  (Much  en' 
treat  it  with  carbon  bisulphide, 

pouring  a  few  ounces  of  the  liquid  in  holes  made  in  the 
nest  and  immediately  stopping  up  the  holes  so  the  gas  will  be 
forced  throughout  the  nest.  Colonies  of  the  house  ants  may 
often  be  treated  with  gasoline  or  boiling  water.  Dilute  car- 
bolic acid  injected  into  the  crevices  through  which  the  ants 
enter  a  room  will  sometimes  drive  them  away.  Oil  of  lemon 
diluted  with  alcohol  will  serve  the  same  purpose  for  some 
species.  When  it  is  impossible  to  destroy  the  nests,  many 
of  the  ants  may  be  trapped  by  putting  out  scraps  of  attrac- 
tive food  or  sponges  wet  with  sweet  syrup.  The  persis- 
tent use  of  such  traps  will  usually  give  relief  from  the 
pests  if  the  baits  are  removed  as  soon  as  they  are  covered 
with  the  ants.  Powdered  borax  spread  around  the  thres- 
hold or  other  places  where  the  ants  enter  will  act  as  a  re- 
pellent. Wood  or  cloth  that  has  been  treated  with  a 


400    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


saturated  solution  of  corrosive  sublimate  will  repel  the  ants 
as  long  as  the  poison  remains.  ''Ant  tape"  is  made  by  soak- 
ing ordinary  cotton  tape  in  a  saturated  solution  of  corrosive 
sublimate.  After  the  tape  is  dry  it  may  be  fastened  around 
table  legs,  on  the  edges  of  shelves  or  in  other  places.  The 
ants  will  not  cross  the  tape  as  long  as  the  poison  remains  on 
it.  It  may  thus  afford  protection  for  several  months  if  kept 
dry.  As  corrosive  sublimate  is  very  poisonous  it  must  not  be 
used  where  children  can  reach  it,  and  care  must  be  taken  to 
wash  the  hands  thoroughly  after  handling  it.  It  has  been 
found  that  the  most  successful  way  to  control  the  Argentine  ant 
is  to  place  a  number  of  sponges  that  have  been  soaked  in  a 
weak  solution  of  arsenic  in  convenient  places  about  the  yard 
or  in  the  houses.  A  gallon  of  this  poison  may  be  prepared 

by  mixing  one-third  of  an  ounce 
of  arsenite  of  soda  in  a  syrup 
that  has  been  made  by  dissolv- 
ing six  pounds  of  sugar  in  a 
gallon  of  water.  This  poison 
acts  very  slowly  and  is  carried 
to  the  nest  by  the  workers  and 
fed  to  the  queen  and  the  young 
so  that  the  whole  colony  may  be 
exterminated  or  driven  away  in 
a  few  weeks.  The  same  remedy 
may  prove  effective  in  fighting 
other  species. 

Clothes -moths. — There  are  two  common  species  of  small 
moths  whose  larvae  attack  woolen  fabrics,  furs  and  feathers. 
The  case-making  clothes-moth,  Tinea  pellionella,  is  very  com- 
mon, particularly  in  the  North.  The  wings  expand  about 
half  an  inch,  the  forewings  are  grayish  yellow  with  indistinct 
fuscous  spots,  and  the  hind  wings  are  grayish.  The  eggs  are 
laid  on  or  near  the  articles  upon  which  the  larvae  are  to  feed. 
As  soon  as  they  hatch  the  larvae  begin  to  construct  little  cases 
or  covers  out  of  bits  of  the  material  on  which  they  are  feeding. 
This  case  is  enlarged  from  time  to  time  as  the  insect  grows. 
There  may  be  two  or  more  generations  in  warm  places. 


FIG.  1 86.— The  clothes-moth, 
Tinea  pellionella;  larva,  larva  in 
case,  and  adult.  (Twice  natu- 
ral size;  after  Howard  and 
Marlatt.) 


INSECTS  AFFECTING  MAN  AND  ANIMALS    401 

The  webbing,  or  southern  clothes-moth,  Tineola  biselliella, 
is  more  abundant  in  southern  latitudes.  It  is  about  the  same 
size  as  the  preceding  species,  and  the  fore  wings  are  uniformly 
pale  ochreous  without  any  markings.  The  larvae  feed  on  al- 
most any  kind  of  dry  animal  tissue,  but  are  especially  de- 
structive to  woolens,  furs,  feathers  and  hair.  They  construct 
no  case,  but  spin  a  cobwebby  path  wherever  they  go  and  when 
ready  to  pupate  make  silken  cocoons. 

Clothing  in  continuous  use  or  carpets  or  hangings  that  are 
frequently  aired  and  dusted,  are  not  troubled  by  these  insects. 
The  woolen  clothes,  furs,  etc.,  that  are  stored  away  for  the 
summer,  and  carpets  or  upholstered  furniture  that  do  not 
receive  regular  and  thorough  cleanings  suffer  most.  If  woolens 
and  furs  are  well  dusted  and  allowed  to  hang  in  the  sun  for  a 
few  hours,  and  are  then  packed  in  tight  paper  boxes  or  wrapped 
carefully  in  linen  they  will  not  be  bothered  by  the  moths. 
Carpets  are  apt  to  become  infested 
along  the  edges  or  under  heavy  furni- 
ture that  is  seldom  moved.  A  liberal 
use  of  gasoline  over  the  infested  areas 
will  kill  the  larvae  that  are  feeding 
there.  Napthaline  flakes  or  "moth 
balls"  act  as  repellants  for  the  moths, 
but  do  not  kill  the  larvae.  The  insects  FIG.  187.— Carpet- 
do  not  breed  in  temperatures  lower  beetle,  or  "buffalo- 
than  40°  F.,  and  valuable  goods  are  j$^  b£'*.3 
often  placed  in  cold  storage  when  it  is  adult.  (After  Howard 

necessary  to  pack  them  away  for  some    an,d  Marlatt;  much 

J  enlarged.) 

time. 

Carpet-beetles.— The  carpet-beetles,  Anthrenus  scroph- 
ularice,  or  "buffalo-moths,"  as  the  larvae  are  sometimes  called, 
feed  on  carpets  and  sometimes  on  other  woolen  goods  that  are 
packed  away.  The  adults  are  small,  broadly  oval,  black 
beetles  that  are  covered  with  minute  black  and  grayish  scales 
which  give  the  insect  a  mottled  appearance.  The  larvae 
have  habits  somewhat  like  those  of  the  clothes  moth  larvae, 
and  may  be  controlled  by  the  same  treatment. 

Some  of  the  insects  that  attack  flour,  meal  and  other  grain 
26 


402    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

products  are  discussed  in  Chapter  XXXVI.  Absolute  cleanli- 
ness will  usually  keep  the  kitchen  and  pantry  free  from  these 
pests.  No  open,  partially-used  packages  should  be  left  for 
breeding  places  for  these  insects. 


CHAPTER  XXXI 
CONTROLLING  INSECT  PESTS 

The  next  nine  chapters  will  be  devoted  to  a  consideration  of 
the  very  important  relations  that  the  insects  bear  to  our 
material  welfare,  in  their  capacity  as  pests  of  our  crops, 
orchards  and  forests.  It  is  estimated  that  the  annual  money 
loss  occasioned  by  insects  in  the  United  States  is  approximately 
as  follows: 

Cereals $300,000,000 

Hay  and  forage 66,500,000 

Cotton 85,000,000 

Tobacco 10,000,000 

Truck  crops 60,000,000 

Sugars 9,500,000 

Fruits 60,000,000 

Farm  forests 11,000,000 

Miscellaneous  crops 10,000,000 

Animal  products 300,000,000 

Natural  forests  and  forest  products 100,000,000 

Products  in  storage 200,000,000 

$1,212,000,000 

This  summary  takes  into  account  only  those  insects  which 
directly  affect  our  crops  or  other  products.  We  might  well  add 
to  this  something  of  the  financial  loss  caused  by  those  insects 
already  discussed,  that  affect  man  himself,  but  this  is  a  much 
more  difficult  problem.  It  has  been  estimated,  for  instance, 
that  we  pay  more  than  $10,000,000  a  year  for  screens  for  our 
houses  to  protect  us  from  mosquitoes  and  flies,  and  yet  this  af- 
fords us  only  a  small  measure  of  protection.  Such  an  amount 
is  comparatively  insignficant  when  compared  to  the  reduced 
value  in  real  estate  because  of  the  mosquitoes  that  infest 
many  regions  making  them  almost  uninhabitable,  or  to  the 

403 


4o4    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

tremendous  financial  loss  resulting  from  the  quarantine  and 
suspension  of  business  which,  until  recent  years,  always  fol- 
lowed an  outbreak  of  yellow  fever  in  any  region. 

Again  we  might  consider  the  great  loss  of  time  and  energy 
that  is  occasioned  by  malaria  in  many  regions.  A  man's 
producing  capacity  may  be  reduced  50  to  75  per  cent,  for  a 
number  of  years  because  of  this  disease.  This,  of  course,  most 
seriously  retards  the  development  of  the  malarial  regions, 
regions  that  might  otherwise  be  producing  millions  of  dollars 
where  they  now  produce  only  hundreds  of  thousands.  It  is 
not  conceivable  that  we  can  make  any  estimate  in  dollars 
and  cents  of  the  great  bodily  and  mental  suffering  entailed 
as  a  result  of  some  of  the  diseases  that  are  carried  by  insects 
and  of  the  hundreds  of  thousands  of  deaths  that  occur  annually 
from  these  diseases.  Yet  these  are  by  far  the  most  important 
factors  to  be  considered  in  estimating  the  economic  importance 
of  insects,  and  the  work  that  is  being  done  along  the  line  of  con- 
trolling the  insects  that  carry  disease  germs  is  the  work  that 
most  demands  the  co-operation  and  support  of  every  citizen. 

In  no  country  in  the  world  are  the  forces  that  are  fighting 
insect  pests  so  well  organized  as  they  are  in  the  United  States. 
The  federal  government  maintains  a  large  and  very  effective 
Bureau  of  Entomology  employing  more  than  one  hundred 
men  most  of  whom  devote  their  whole  time  to  the  study  of  the 
insect  pests  and  methods  of  controlling  them.  Nearly  all 
states  have  their  State  Entomologists,  who  may  or  may  not  be 
connected  with  the  state  agricultural  colleges  and  experiment 
stations,  and  many  other  horticultural  officers  and  inspectors 
who  devote  a  large  part  of  their  time  to  the  study  and  control 
of  insects. 

We  cannot  fight  insects  successfully  without  some  knowl- 
edge of  their  structure  and  habits  and  life-history.  More 
than  this,  we  must  know  something  of  their  relation  to  other 
insects  and  other  animals.  So  the  study  of  economic 
entomology  includes  attention  to  systematic  and  morphologic 
and  ecologic  entomology.  It  is  a  much  more  comprehensive 
study  than  it  is  perhaps  popularly  supposed  to  be. 

Government  entomologists  really  devote  a  large  part   of 


CONTROLLING  INSECT  PESTS  405 

their  time  to  the  study  of  the  general  biology  of  insects,  and 
many  of  their  bulletins  and  special  reports  are  scientific  papers 
of  much  value  to  naturalists,  as  well  as  to  the  general  public, 
for  whom  they  are  primarily  issued.  Directions  for  obtaining 
these  bulletins  and  reports  are  given  on  page  419. 

Sometimes  the  fight  against  an  insect  pest  can  be  carried  on 
successfully  by  one  man  in  his  own  orchard  or  field,  but  more 
often  the  whole  community  must  co-operate  if  lasting  benefits 
are  to  be  secured,  because  most  of  the  insects  so  readily  pass 
from  one  place  to  another.  The  necessity  for  such  co-opera- 
tion is  well  illustrated  in  the  fight  against  flies  and  mosquitoes. 
One  unclean  stable,  where  the  manure  is  left  for  a  breeding  place 
for  flies,  may  be  a  source  of  annoyance  and  danger  to  all  the 
homes  in  the  community.  For  a  successful  campaign  against 
house-flies,  all  the  members  of  the  community  must  see  to  it 
that  there  are  no  manure  piles,  open  privy  vaults,  open  garbage 
cans  or  other  places  where  the  flies  may  breed  and  feed,  while 
a  united  effort  should  be  made  to  trap  and  kill  as  many  of  the 
adult  flies  as  possible.  Some  mosquitoes,  such  as  the  yellow- 
fever  mosquito  and  others,  breed  only  near  houses  and  fly  but 
a  short  distance.  In  such  instances  a  "single  person  may  free 
his  house  from  these  pests  by  seeing  that  the  mosquitoes 
find  no  breeding  places  near.  But  many  kinds  of  mosquitoes 
fly  for  considerable  distances,  and  the  problem  of  their  control 
then  becomes  one  for  the  community  as  a  whole  to  deal  with. 

NATURAL  ENEMIES  OF  INSECTS 

Insects  have  many  natural  enemies  which  in  many  ways  help 
to  control  the  injurious  species.  Indeed,  were  it  not  for  this 
condition  many  of  them  would  increase  so  rapidly  that  they 
would  be  wholly  beyond  the  control  of  man.  It  is  a  significant 
fact  that  with  all  our  improved  methods  for  fighting  insects  the 
total  amount  of  damage  that  they  do  to  our  crops  is  increasing 
rather  than  decreasing.  This  is  due  in  part  to  the  introduction 
of  new  pests,  and  in  part  to  the  more  extensive  and  intensive 
cultivation  of  crops.  But  the  fact  that  we  are  changing  the 
natural  conditions  of  vast  areas  and  often  destroying  many  of 


4o6    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  natural  enemies  of  some  of  the  insects,  and  thus  upsetting 
the  balance  that  had  been  established  in  nature,  is  accountable 
for  a  large  measure  of  this  increase. 

The  part  that  birds  play  in  the  control  of  the  insect  pests  of 
forest,  orchard,  garden  and  field  is  of  much  more  importance 
than  is  usually  realized.  Many  species  of  birds  feed  chiefly 
upon  insects.  From  an  examination  of  the  stomach  contents 


FIG.  1 88. — Phoebe,  a  well  known  flycatcher,  90  per  cent,  of  whose  food 
consists  of  insects. 

of  large  numbers  of  birds  it  has  been  estimated  that  insects 
form  about  96  per  cent,  of  the  food  of  flycatchers  in  some 
regions,  95  percent,  of  the  food  of  wrens,  94  per  cent,  of  warblers, 
65  per  cent,  of  woodpeckers  and  meadow-larks,  and  more  than 
25  per  cent,  of  the  native  sparrows.  Swifts,  swallows,  titmice, 
crows,  jays,  blackbirds  and  many  others  feed  largely  on  in- 
sects. As  many  as  3000  to  5000  insects  have  been  taken  from 
the  stomach  of  a  single  bird.  Of  course  many  beneficial  insects 
are  eaten  with  the  injurious  ones,  and  some  of  the  birds  also 
take  toll  of  fruit  in  the  orchard  or  grain  in  the  field  but  with 


CONTROLLING  INSECT  PESTS 


407 


the  notable  exception  of  the  introduced  English  sparrow  and 
of  the  few  species  of  native  sap-suckers,  and  two  kinds  of 
hawks,  practically  all  of  our  birds  are  to  be  regarded  as  friends 
and  helpers  on  the  farm  or  in  the  orchard. 

The  common  garden  toads  eat  many  insects  and  worms 
during  the  evenings  while  they  are  feeding.  Spiders  trap  and 
destroy  many  of  the  smaller  insects  and  are  especially 
serviceable  on  small  flowering  bushes  and  garden  plants. 

But  it  is  to  the  insects  them- 
selves that  we  must  look  for  some 
of  the  most  destructive  enemies 
of  others  of  their  class.  It  will 
be  convenient  in  considering 
these  to  divide  them  into  two 
groups;  first  the  predaceous  in- 
sects, which  run  or  fly  about 
attacking  and  devouring  other 
insect  species,  and,  second,  the 
parasitic  insects,  which  spend  a 
part  or  all  of  their  lives  in  or  on 
the  body  of  their  hosts. 

Among  the  predaceous  insects 
the  ladybird-beetles  are  per- 
haps the  most  important,  as  in  both  the  adult  and  larval 
stages  they  destroy  great  numbers  of  plant-lice,  scale-insects 
and  other  noxious  insects.  A  remarkable  example  of  the  good 
that  they  may  do  is  furnished  by  the  Australian  ladybird- 
beetle,  Novius  cardinalis,  that  was  introduced. into  California 
to  aid  in  controlling  the  cottony-cushion  scale,  Icerya  purchasi, 
a  pest  that  threatened  the  destruction  of  the  citrus  fruit  in- 
dustry in  California.  So  rapidly  did  the  beetles  multiply 
and  so  effectively  did  they  do  their  work  that  the  scale  was 
soon  under  control  and  is  no  longer  regarded  as  a  serious  pest. 
Many  other  species  of  ladybird-beetles  have  been  introduced 
into  this  country,  but  none  has  been  so  successful  in  its  work  as 
this  one. 

Many  of  our  native  species  of  ladybird-beetles  are  par- 
ticularly destructive  to  certain  kinds  of  aphis  and  scale-insects. 


FIG.  189. — A  ladybird-beetle, 
Coccinella  calif  arnica;  larva, 
pupae,  and  adult  on  Lawson's 
cypress.  (Twice  natural  size.) 


408    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

In  California  millions  of  living  ladybird-beetles  are  gathered 
each  winter,  while  hibernating  in  great  masses  in  the  high 
Sierras,  and  as  soon  as  the  aphids  begin  to  appear  in  destructive 
numbers  in  the  melon  fields  and  other  places  large  shipments  of 
the  beetles  are  sent  to  the  infested  regions. 

The  larvae  of  the  lace-winged-flies  and  the  syrphus-flies  are 
also  great  enemies  of  aphis  and  other  soft-bodied  insects. 
The  predaceous  ground-beetles  (family  Carabida)  and  the 
tiger-beetles  (family  Cincindelidce)  destroy  many  larva?  and 


FIG.  190. — The  fluted  scale,  I  eery  a  purchasi,  attacked  by  the  Australian 
ladybird-beetle,  Novius  cardinalis.  In  .the  lower  left-hand  corner,  a 
Novius  which  has  just  issued  from  its  pupal  case.  (Upper  figure  slightly 
enlarged;  lower  figure  much  enlarged.) 

adult  insects  that  can  be  captured  on  the  ground.  The 
assassin-bugs  (family  Reduviida)  are  all  predaceous,  as  are 
several  other  kinds  of  Hemiptera,  We  have  already  called 
attention  to  the  importance  of  dragon-flies  in  controlling 
mosquitoes. 

Among  the  parasitic  insects  the  tachina-flies  (family 
Tachinida)  rank  high  as  enemies  of  variouskinds  of  caterpillars. 
The  eggs  are  usually  laid  on  the  body  of  the  insect  into  which 
the  young  make  their  way  as  soon  as  they  are  hatched.  Here 
they  feed,  often  without  destroying  the  host  until  it  pupates. 
Sometimes  the  eggs  of  the  tachina-flies  are  laid  on  the  leaves, 


CONTROLLING  INSECT  PESTS 


409 


and  leaf-feeding  larvae  take  the  eggs  into  their  alimentary  canal 
where  they  hatch.     The  parasites  then  bore  their  way  into  the 


FIG.  191. — -A  preda- 
ceous  g  r  o  u  n  d-b  e  e  1 1  e, 
Calosoma  sycophanta. 
(Natural  size.) 


FIG.  192. — A  tachina-fly, 
Blepharipeza  adusta,  the  larva 
of  which  is  an  internal  para- 
site. (About  twice  natural 
size.) 


body  tissues  of  the  host.  The  parasitic  Hymenoptera,  which 
include  some  of  the  best  known  and  most  important  of  the 
parasites  and  which  comprise  hundreds  of  different  kinds, 


. 

^/^4|^u 


FIG.   193. — Braconid  cocoons  on  a  caterpillar  that  has  been  killed  by  the 
parasites.     (About  natural  size.) 

each  attacking  its  own  particular  single  or  few  host  kinds, 
have  been  discussed  in  Chapter  XVII. 


4io    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


The  most  extensive  experiment  in  attempting  to  control  a 
serious  insect  pest  by  its  insect  enemies  is  the  work  that  is  now 


FIG.  194.  FIG.  195. 

FIG.  194. — Aphids  on  a  leaf,  which  have  been  parasitized  by  a  Braconid 
parasite.  (About  natural  size.) 

FIG.  195. — Larvas  and  pupae  of  the  oak  tree  moth,  Phryganidia  califor- 
nica,  that  have  been  killed  by  a  disease  caused  by  bacteria.  (Natural 
size.) 

being  carried  on  by  the  Bureau  of  Entomology  in  the  fight 
against  the  gipsy-moth  in  the  New  England  states.     The  way 


CONTROLLING  INSECT  PESTS  411 

in  which  this  insect  was  introduced  and  the  damage  that  it  does 
is  referred  to  on  page  507.  Trained  entomologists  have  been 
sent  to  every  foreign  land  where  the  gipsy-moth  is  known  to 
occur,  and  they  have  gathered  and  sent  to  this  country  all  of 
the  different  insect  enemies  of  the  pest  that  they  could  dis- 
cover. Some  of  these  have  proved  to  be  of  no  effect  in  our  coun- 
try, others  aid  a  little,  and  still  others  give  promise  of  being 
important  factors  in  the  control  of  the  moth.  Those  in  charge 
of  the  work  do  not  expect  to  be  able  to  find  any  one  insect  that 
will  do  for  the  gipsy-moth  what  the  Australian  ladybird- 
beetle  did  for  the  cottony-cushion  scale,  but  they  do  expect  that 
if  they  introduce  a  great  many  parasitic  and  predaceous  kinds 
enough  of  them  may  work  together  to  check  the  slow  spread  of 
the  pest  and  finally  control  it. 

Insects  are  often  attacked  by  fungi  and  by  certain  bacterial 
diseases.  Sometimes  these  are  very  important  factors  in  con- 
trolling outbreaks  of  chinch-bugs,  scale-insects,  grasshoppers, 
various  larvae  and  other  insects.  But  the  conditions  which 
favor  the  development  of  the  fungi  or  bacteria  are  often  beyond 
our  control,  and  usually  there  is  but  little  that  we  can  do  to 
aid  in  the  spread  of  these  diseases. 

PREVENTIVE  METHODS  OF  CONTROL 

The  natural  enemies  of  insects  do  much,  indeed,  toward 
controlling  their  numbers,  but  some  of  the  worst  pests  require 
the  constant  attention  of  the  farmer  or  orchardist  or  he  soon 
sees  his  crops  badly  injured  or  totally  destroyed.  We  can 
never  hope  to  get  rid  entirely  of  some  of  the  pests,  but  by  careful 
management  they  may  be  kept  in  check  so  that  they  may  not 
reap  the  lion's  share  of  the  harvest.  The  most  important 
thing  in  dealing  with  insects  is  to  begin  early.  Too  often  when 
a  pest  makes  its  appearance  the  orchardist  waits  for  a  more 
convenient  season  to  commence  fighting  it.  Meantime  the 
insect  has  had  a  chance  to  lay  its  eggs  or,  perhaps,  to  produce 
several  generations  thus  increasing  many  fold  the  number  that 
must  now  be  fought.  Until  one  understands  how  very  rapidly 
many  insects  multiply  one  can  hardly  realize  the  importance  of 
trying  to  get  rid  of  a  pest  just  as  soon  as  it  is  found  in  the 


4i2    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

orchard  or  field.  It  is  usually  much  easier  and  cheaper  to 
prevent  an  insect  from  getting  a  start  in  the  orchard  or  garden 
than  it  is  to  fight  it  after  it  has  gained  a  firm  foothold.  "An 
ounce  of  prevention  is  worth  a  pound  of  cure." 

Among  the  most  effective  means  of  preventing  insect  injury 
may  be  mentioned  the  following: 

High  Cultivation. — This  not  only  makes  the  tree  or  other 
plant  yield  its  best  returns  but  it  is  a  well  known  fact  that  a 
strong  healthy  plant  is  not  nearly  as  apt  to  be  attacked  by  as 
many  insect  pests  as  one  that  is  already  weakened  or,  if  it  is 
attacked,  it  is  able  to  stand  much  more  injury  without  the 
effect  being  shown  in  the  crop  it  yields.  The  first  and  best 
way  of  fighting  insect  pests  is  then  to  keep  the  plant  in  the 
very  best  condition  possible  by  high  cultivation,  judicious 
pruning,  fertilizing,  etc. 

Clean  Culture. — Many  of  the  most  injurious  insects  pass  the 
winter  months  under  rubbish  of  various  kinds  that  lies  scattered 
over  the  farm.  If  this  rubbish  is  not  allowed  to  accumulate 
such  insects  will  be  more  likely  to  perish  during  the  winter. 
Keeping  clean  will  also  reduce  the  opportunities  for  feeding  and 
breeding  and  allow  a  more  thorough  application  of  insecticides. 
In  orchards  this  recommendation  for  clean  culture  is  of  especial 
importance.  Many  insects  breed  and  complete  their  develop- 
ment in  dead  wood  or  fallen  fruit,  others  pass  the  winter  months 
or  lay  their  winter  eggs  upon  the  smaller  branches  of  the  trees. 
If  the  orchardist  would  take  the  pains  to  trim  out  and  burn  all 
the  dead  and  infected  branches,  and  to  see  that  all  fallen  fruit 
was  destroyed,  there  would  be  little  complaint  of  some  of  the 
insects  that  are  now  serious  pests. 

Crop  Rotation. — Many  insects  live  only  on  one  kind  of  plant, 
and  when  not  able  to  find  this  plant  they  perish  or  are  scattered 
so  as  to  do  little  damage.  This  fact  may  often  be  taken 
advantage  of  by  a  system  of  crop  rotation. 

Protection  of  Plants. — Many  small  plants,  especially  in  the 
garden,  may  be  protected  by  screens  or  other  devices  for 
keeping  the  pests  away  from  the  plants. 

Late  Plowing. — Many  insects  may  be  killed  or  exposed  to 
their  enemies  by  plowing  the  field  late  in  the  fall.  Some  of 


CONTROLLING  INSECT  PESTS  413 

the  wire-worms  and  the  eggs  of  grasshoppers  and  other  pests 
are  thus  destroyed.  Late  plowing  of  fallow  lands  is  especially 
important,  as  there  are  usually  many  insects  in  such  fields. 

Trap  Crops. — It  is  sometimes  profitable  to  plant  a  crop  that 
is  attractive  to  the  insects  that  are  to  be  combated  and  after 
the  insects  have  gathered  there,  to  destroy  the  whole  crop  by 
burning  or  plowing  it  under  or  spraying  it  with  some  insecti- 
cide that  will  kill  the  insects.  In  this  way  the  main  planting 
of  the  same  or  other  crops  may  be  left  comparatively  free  from 
the  pests. 

ACTIVE  METHODS  OF  CONTROL 

In  spite  of  all  our  care  and  precautionary  measures,  however, 
many  pests  \vill  certainly  become  established  in  the  orchard  or 
garden  or  field,  and  then  the  fight  must  be  waged  against  the 
insects  themselves. 

Hand-picking. — This  is  often  the  simplest  way  of  getting  rid 
of  many  of  the  larger  insect  pests.  Large  caterpillars,  like  the 
tomato-worm  and  the  larvae  of  other  moths,  are  easily  seen 
and  destroyed.  Tent-caterpillars  are  also  best  fought  by 
gathering  them  after  they  have  collected  in  their  "tents"  and 
crushing  or  burning  them.  In  the  fall  or  winter  the  eggs 
of  such  moths  as  the  tussuck-moth  are  easily  gathered  and 
destroyed. 

Trapping,  etc. — Insects  may  often  be  found  collected  in  con- 
siderable numbers  under  loose  boards  or  boxes  scattered  over 
the  field.  If  such  places  be  examined  occasionally  many  injuri- 
ous insects  can  be  destroyed.  The  larvae  of  certain  moths,  as 
the  codling-moth,  pupate  in  any  sheltered  place  they  find  on 
the  trunk  of  the  tree.  Advantage  may  be  taken  of  this  habit 
by  placing  a  band  of  burlap  around  the  tree.  Under  this  the 
larvae  collect  and  they  may  easily  be  destroyed.  The  use  of 
lights  in  the  field  to  attract  moths  is  more  or  less  successful  in 
some  places.  Numbers  of  cut-worm  moths  may  thus  be 
destroyed.  Codling-moths  are  not  attracted  to  these  lights. 

Insecticides. — The  most  widely  used  and  perhaps  the  most 
effective  method  of  fighting  insect  pests  after  they  have  obtained 
a  foothold  in  the  orchard,  is  the  use  of  insecticides,  or  insect 


414    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

poisons.  These  may  be  considered  under  four  heads:  first,  the 
internal  poisons,  or  those  which  take  effect  by  being  eaten  along 
with  the  ordinary  food  of  the  insect;  second,  the  contact  in- 
secticides that  kill  the  insects  when  applied  directly  to  their 
body;  third,  the  gases  that  are  used  for  fumigation,  and,  fourth, 
various  substances  that  act  as  repellents.  The  kind  of  insec- 
ticide to  be  used  depends  in  a  large  degree  upon  the  structure 
of  the  mouth-parts  of  the  insects.  For  beetles,  the  larvae  of 
moths  and  butterflies,  and  others  with  biting  mouth-parts 
the  internal  poisons  are  used,  while  for  the  various  insects 
with  sucking  mouth-parts,  as  the  plant-lice,  scale-insects,  etc., 
the  contact  insecticides  are  used.  The  reason  for  this  is  very 
plain.  It  would  be  useless  to  spray  a  plant  with  poison  when 
it  was  infested  by  an  insect  with  sucking  mouth-parts,  for 
such  insects  obtain  their  food  from  the  juices  of  the  plant 
which  are  not  reached  at  all  by  the  poison.  But  if  the  plant 
is  infested  by  biting  insects,  such  an  application  of  poison  to 
all  the  leaves  and  tender  shoots  would  be  effective,  for  with 
each  bitten  off  and  swallowed  mouthful  of  leaf,  the  insect  would 
get  a  dose  of  the  poison. 

Internal  Poisons. — Paris  green  was  for  a  long  time  regarded 
as  the  most  efficient  of  the  internal  poisons  and  is  still  used  to  a 
limited  extent. 

The  poison  is  applied  as  a  spray,  using  one  pound  of  Paris 
green  to  150  to  200  gallons  of  water  for  such  trees  as  apples, 
pears,  etc.  For  peach  and  plum  trees  and  other  plants  with 
delicate  foliage  which  is  very  susceptible  to  the  poison  the 
mixture  should  not  be  stronger  than  one  pouud  of  Paris  green 
to  250  or  300  gallons  of  water.  A  pailful  or  two  of  fresh  lime 
water  should  be  added  to  every  200  gallons  of  the  mixture  to 
prevent  the  poison  from  scalding  the  foliage.  In  preparing 
the  mixture  the  Paris  green  should  first  be  mixed  into  a  fine 
paste  with  a  small  amount  of  water;  it  should  then  be  strained 
thoroughly  and  the  bulk  of  water  added.  The  lime  may  be 
added  to  the  paste  before  straining,  in  amount  equal  to  the 
amount  of  poison  used,  instead  of  being  added  to  the  mixture  as 
above  recommended.  The  mixture  must  be  kept  well  stirred 
during  the  spraying. 


CONTROLLING  INSECT  PESTS  415 

For  fighting  such  insects  as  cut-worms  and  grasshoppers 
a  bran  mash  poisoned  with  Paris  green  is  often  very  effective. 
This  may  be  made  as  follows:  thoroughly  mix  one  pound  of 
Paris  green  with  twenty-five  pounds  of  bran  or  middlings 
and  moisten  with  about  a  gallon  of  water  which  has  been  sweet- 
ened by  adding  one  or  two  quarts  of  cheap  molasses.  This  will 
make  a  stiff  mash  that  may  be  placed  in  the  affected  field,  a 
tablespoonful  or  so  in  a  place. 

For  most  purposes  arsenate  oj  lead  is  now  used  instead  of 
Paris  green.  It  is  less  injurious  to  the  foliage,  remains  in 
suspension  longer,  and  in  many  other  ways  is  better  than  Paris 
green.  It  may  be  manufactured  at  home,  but  it  is  usually 
safer  to  buy  some  of  the  reliable  brands  that  are  on  the  market. 
It  comes  in  two  forms,  as  paste  and  powder.  Four  to  ten 
pounds  of  the  paste,  or  two  to  five  pounds  of  the  powder, 
are  used  with  every  100  gallons  of  water.  The  spraying  should 
be  so  thoroughly  done  that  all  the  foliage  and  fruit  is  covered 
with  a  thin  film  of  the  poison.  Some  fungicide,  such  as  Bor- 
deaux mixture  or  sulphur -lime,  is  of  ten  used  in  connection  with 
this  insecticide,  and  the  trees  are  thus  freed  from  their  insect 
pests  and  fungus  diseases  with  one  spraying.  A  gallon  of  mo- 
lasses or  twenty- five  pounds  of  glucose  is  often  added  to  every 
loo  gallons  of  the  spray  when  arsenate  of  lead  is  used  for  flea- 
beetles  and  other  leaf-feeding  insects  on  cabbages,  turnips,  etc. 

White  hellebore  is  often  used  instead  of  arsenic,  especially 
in  the  garden.  It  may  be  applied  dry,  diluted  with  five  or  ten 
parts  of  flour,  or  it  may  be  used  as  a  spray,  one  ounce  to  a 
gallon  of  water. 

Contact  Insecticides. — Of  the  many  contact  insecticides 
used,  the  sulphur-lime  solution  is,  in  many  respects,  the  best. 
It  acts  quickly  on  the  scaly  covering  of  such  insects  as 
the  San  Jose  scale  and  soon  kills  the  insect.  It  has  the  addi- 
tional advantage  of  being  an  excellent  fungicide  as  well  as  an 
insecticide.  There  are  many  brands  of  concentrated  sulphur- 
lime  solution  on  the  market,  and  most  orchardists  now  prefer 
to  buy  some  of  these  rather  than  prepare  the  mixture  them- 
selves. In  using  these  all  that  is  necessary  is  to  add  water  and 
apply  thoroughly  with  the  spray  pump.  The  strength  of  the 


4i6    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

various  commercial  brands  varies  somewhat  but  as  a  rule  nine 
to  twelve  gallons  of  the  concentrated  solution  to  100  gallons  of 
water  should  be  used  in  treating  trees  in  the  winter  for  such 
insects  as  San  Jose  scale  and  blister-mites.  For  use  in  the 
summer  for  fungus  and  soft-bodied  insects,  such  as  aphids 
and  young  scale-insects,  the  proportion  should  be  about 
two  or  three  gallons  of  the  concentrated  solution  to  100  gallons 
of  water.  It  has  recently  been  demonstrated  that  in  some 
instances  sulphur-lime  solution  jnay  take  the  place  of  arsenical 
sprays  as  it  acts  as  a  stomach  poison  as  well  as  a  contact  in- 
secticide. Sulphur-lime,  three  gallons  to  100  gallons  of  water, 
has  been  used  with  some  success  in  controlling  the  codling 
moth.  The  addition  of  a  little  arsenate  of  lead  will  probably 
be  found  advisable. 

It  is  somewhat  difficult  to  prepare  sulphur-lime  wash  with 
uniformity  unless  one  is  well  prepared  for  this  work.  The 
best  plan  is  to  obtain  one  of  the  bulletins  issued  by  the  state 
in  which  the  orchardist  lives,  and  follow  carefully  the  directions 
given  there.  The  following  formula  is  one  that  is  often  used: 

Unslaked  lime 5  pounds 

Flowers  of  sulphur n  pounds 

Water 5  gallons 

Put  a  little  of  the  water  in  a  kettle  or  boiler  over  a  good  fire; 
add  the  lime  and  after  it  has  started  to  slake  sift  the  sulphur 
over  it  adding  enough  water  to  maintain  a  thin  paste.  After 
the  slaking  and  mixing  are  completed  add  more  water  and  boil 
for  about  one  hour  adding  enough  water  from  time  to  time  to 
make  up  for  evaporation.  If  properly  made  the  mixture  will 
be  of  an  amber  color,  and  there  will  be  but  little  sediment. 
This  is  a  concentrated  solution  which,  before  using,  should  be 
diluted  to  the  strength  indicated  above. 

Kerosene  emulsions  or  distillate  oil  emulsions  are  often  used 
for  many  of  the  soft-bodied  sucking  insects.  The  follow- 
ing is  the  standard  formula  for  kerosene  emulsion:  kerosene 
2  gallons;  soap  (preferably  whale-oil  soap)  1/2  pound;  water 
i  gallon.  The  soap  should  be  dissolved  in  the  water  heated  to 
boiling  and  the  kerosene  then  added.  Churn  or  otherwise 


CONTROLLING  INSECT  PESTS  417 

thoroughly  mix  the  kerosene  and  soapsuds  until  a  thick  emul- 
sion is  formed  which  will  set  on  cooling.  When  needed  mix  one 
part  of  this  emulsion  with  twelve  parts  of  water  and  spray 
over  the  insects. 

The  distillate-oil  emulsion  can  only  be  made  satisfactorily 
with  a  power  sprayer.  The  proportions  are:  distillate  oil  20 
gallons,  fish  oil  or  whale-oil  soap  30  pounds,  hot  water  12 
gallons.  Five  and  one-half  gallons  of  the  emulsion  should  be 
used  to  each  100  gallons  of  water  when  spraying  for  such  in- 
sects as  thrips.  About  a  pint  of  strong  tobacco  extract 
added  to  each  200  gallons  of  diluted  distillate  oil  emulsion 
adds  much  to  its  efficiency  as  a  spray  for  thrips. 

There  are  several  miscible  oils  on  the  market  under  various 
trade  names.  These  are  convenient  to  use  because  they  readily 
mix  with  water.  The  proportions  to  use  for  the  winter  and 
summer  sprayings  are  generally  indicated  on  the  package 
containing  the  oils. 

Resin  sprays  are  still  used  in  some  regions,  particularly  for 
white-flies  on  citrus  trees.  The  following  formula  has  proved 
satisfactory:  resin  20  pounds,  caustic  soda,  pulverized,  7 
pounds,  fish  oil  3  1/2  pints.  Boil  together  in  a  little  water  and 
finally  add  enough  water  to  make  100  gallons. 

A  carbolic  acid  emulsion,  made  by  adding  i  gallon  of  crude 
carbolic  acid  to  eight  pounds  of  whale-oil  soap  that  has  been 
dissolved  by  boiling  in  eight  gallons  of  water,  makes  a  good 
stock  solution  for  sprays  for  aphis,  mealy-bugs  and  other  soft- 
bodied  insects.  For  use  add  twenty  gallons  of  water  to  every 
gallon  of  the  emulsion. 

Whale-oil  soap  or  common  laundry  soap  are  often  used  for 
spraying  for  aphids  or  other  soft-bodied  insects. 

Tobbacco  extracts  and  nicotine  solutions  are  sometimes  very 
efficient  when  used  by  themselves  or  in  connection  with  some 
other  material. 

There  are  several  mixtures  that  are  used  for  dipping  animals 
infected  with  ticks  or  mites.  Sulphur-lime,  crude  oil,  white 
arsenic,  tobacco  and  other  substances  are  used  for  this  purpose. 
As  the  use  of  most  of  these  is  attended  with  more  or  less  danger 
unless  properly  done  the  detailed  directions  given  in  some  of 
27 


4i8    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  recent  government  and  experiment  station  bulletins 
should  be  consulted.  (See  p.  419). 

Pyrethrum,  Persian  insect  powder,  or  buhach,  is  a  powder 
made  by  pulverizing  the  flowers  of  pyrethrum.  It  gives  off 
a  volatile  oil  which  is  poisonous  to  insects  but  does  not  affect  the 
higher  animals.  It  is  used  principally  as  a  household  remedy, 
where  it  can  be  dusted  on  or  near  the  insects. 

Gases. — As  the  citrus  trees  and  some  others  have  a  very 
dense  foliage  and  retain  their  leaves  the  year  round  it  is  difficult 
to  spray  them  with  the  ordinary  insecticides.  When  it  is 
necessary  to  treat  them  for  insect  pests  they  are  usually  fumi- 
gated with  hydrocyanic  acid  gas,  which  is  generated  under  a  tent 
that  is  placed  over  the  tree.  Nine  ounces  of  water  are  placed 
in  an  earthenware  vessel  and  three  ounces  of  sulphuric  acid 
added;  then  three  ounces  of  potassium  cyanide  are  dropped 
into  the  liquid  and  the  tent  quickly  closed  as  the  gas  that  is 
immediately  generated  is  deadly  to  all  animal  life.  The 
amount  of  gas  necessary  to  kill  all  the  insects  on  the  tree  varies 
with  the  species  of  insects  and  the  size  of  the  tree.  Careful 
tables  are  given  in  government  and  state  bulletins  relating  to 
this  subject. 

Nursery  trees  that  are  infested  with  scale-insects  or  other 
pests  may  be  placed  in  a  tight  bin  or  a  fumigating  house  and 
given  a  thorough  treatment  with  this  gas.  It  is  also  some- 
times used  in  greenhouses  for  scale-insects,  aphids,  etc.,  and  in 
mills  that  have  become  infested  with  the  Mediterranean  flour 
moth  or  other  pests.  This  gas  is  sometimes  used  to  kill 
household  pests  such  as  bedbugs,  cockroaches,  etc.,  but  as  it  is 
very  dangerous  it  should  never  be  used  except  by  some  ex- 
perienced person. 

Carbon  bisulphide  is  used  in  killing  insects  in  stored  grain 
and  sometimes  also  in  treating  subterranean  insects.  It  is 
bought  and  used  as  a  liquid  which  volatilizes  into  a  heavy,  ill- 
smelling  gas  which  is  not  quite  as  deadly  as  hydrocyanic  gas 
but  is  so  strong  that  large  doses  prove  fatal  to  all  animal  life. 
It  can  be  used  in  closets  infested  by  clothes-moths  by  exposing 
some  of  the  liquid  in  a  saucer  on  the  floor,  (better  on  a  shelf  as 
the  fumes  are  heavier  than  air  and  sink  rather  than  rise)  and 


CONTROLLING  INSECT  PESTS  419 

closing  the  door  and  cracks  of  the  closet.  Or  infested  cloth- 
ing may  be  put  into  a  tight  trunk  or  box  together  with  a  small 
saucer  of  the  liquid.  It  is  highly  explosive  and  must  never  be 
used  in  the  presence  of  any  artificial  light. 

When  sulphur  is  burned,  very  poisonous  fumes,  mostly 
sulphur  dioxide,  are  given  off.  This  gas  is  fatal  to  all  animal 
life  and  is  sometimes  used  in  fumigating  rooms  or  other  en- 
closed spaces  that  are  infested  with  insects.  Under  the  head 
of  "  Clayton  gas"  it  has  recently  been  much  used  for  fumigating 
ships  and  ship's  cargoes  to  kill  the  rats  and  insects  that  are  so 
often  found  in  the  holds.  It  is  very  penetrating  and  effective 
but  is  usually  objectionable  on  account  of  its  strong  bleaching 
properties  especially  in  the  presence  of  moisture.  Seeds  treated 
with  this  gas  will  not  germinate. 

Repellents. — There  is  a  popular  belief  that  any  ill-smelling 
substance  will  keep  insects  away  from  plants.  While  this  is 
not  wholly  true  there  are  some  substances  which  when  applied 
to  a  plant  seem  to  afford  it  more  or  less  immunity  from  the 
attacks  of  certain  insects.  Bordeaux  mixture,  crude  carbolic 
acid  and  thick  soap  washes  are  among  the  most  effective  of 
such  substances  and  the  various  proprietary  repellant  mixtures 
that  are  on  the  market  usually  depend  on  one  or  more  of  these 
substances  for  their  usefulness.  As  a  general  rule  but  little 
reliance  can  be  placed  on  them. 

How  TO  OBTAIN  STATE  AND  GOVERNMENT  PUBLICATIONS 

Frequent  reference  has  been  made  and  will  be  made  in  the 
following  chapters  to  various  reports  or  bulletins  issued  by 
state  officials  or  by  the  United  States  Department  of  Agricul- 
ture. Some  of  these  are  technical  in  character  and  intended 
for  special  students  but  most  of  them  are  written  for  the  general 
public  and  give  in  a  clear  concise  manner  the  results  of  the 
latest  studies  and  investigations  on  the  subjects  discussed. 

The  reports  and  bulletins  of  the  various  State  Agricultural 
Experiment  Stations  can  be  had  by  applying  to  the  director  of 
the  station  in  whatever  city  this  station  is  situated.  When 
making  application  for  such  bulletins  the  applicant  should  state 


420    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  particular  subjects  in  which  he  is  interested,  and  any 
available  publications  on  that  subject  will  be  forwarded  to 
him.  In  a  few  states  the  State  Entomologist  is  not  an  officer  of 
the  Experiment  Station.  In  such  instances  applications  for 
his  publications  should  be  directed  to  the  State  Entomologist. 
His  office  is  usually  in  the  capital  city.  Some  states  maintain 
a  State  Board  of  Horticulture  or  Agriculture  which  issues 
reports  or  bulletins  that  are  often  of  great  interest. 

Most  of  the  government  bulletins  are  also  for  free  distribu- 
tion. Each  month  the  office  of  Experiment  Stations  issues  a 
list  of  the  publications  that  have  been  published  during  the 
preceding  month.  This  "Monthly  List  of  Publications"  is 
sent  regularly  to  all  who  apply  for  it.  Address  the  Editor  and 
Chief  of  the  Division  of  Publications,  U.  S.  Department  of 
Agriculture,  Washington,  D.  C.  Only  a  limited  number  of 
each  issue  of  many  of  the  government  publications  is  available 
for  free  distribution.  When  this  supply  is  exhausted  the 
publication  may  be  had  by  applying  to  the  Superintendent  of 
Documents,  Washington,  D.  C.  A  small  charge,  usually  only 
five  to  twenty  cents  for  bulletins,  is  made  by  this  office.  On 
request  the  Superintendent  of  Documents  will  mail  a  price-list 
of  all  the  government  publications  relating  to  entomology, 
ornithology,  agriculture  or  any  other  subject. 

The  Division  of  Publications  has  recently  issued  a  very 
helpful  circular  (No.  19)  giving  a  list  of  the  "Publications  of 
the  United  States  Department  of  Agriculture  Classified  for  the 
Use  of  Teachers."  This  may  be  had  by  applying  to  the 
Editor  and  Chief  of  the  Division. 

The  Department  of  Agriculture  also  issues  a  series  of 
"Farmers'  Bulletins"  and  a  "Year  Book,"  both  of  which 
contain  a  great  deal  of  interesting  and  useful  information  on 
many  topics  relating  to  agriculture. 

The  Farmers'  Bulletins  may  be  had  by  applying  to  the 
Secretary  of  Agriculture.  The  Year  Books  can  usually  be 
more  readily  obtained  by  applying  to  the  congressman  repre- 
senting the  district  in  which  the  applicant  lives.  The  congress- 
man may  also  supply  the  Farmers'  Bulletins. 


CHAPTER  XXXII 
INSECTS  INJURIOUS  TO  ORCHARD  TREES 

It  is  estimated  by  careful  and  expert  observers  that  insect 
pests  take,  each  year,  about  one-fifth  of  the  American  fruit 
crop.  This  is  an  annual  money  loss  to  the  growers,  and  to  the 
nation,  of  about  sixty  million  dollars.  A  large  part  of  this 
loss  can  be  prevented. 

The  orchard  pests  include  insects  of  many  kinds,  repre- 
senting different  orders,  and  varying  greatly  in  life  history, 
habits  and  structure.  The  injury  to  the  trees  may  be  to  the 
roots,  the  trunk,  the  leaves,  the  flower  buds,  or  the  fruit. 
Apple  trees,  for  example,  have  their  roots  attacked  by  the 
woolly-aphis,  their  trunks  mined  by  the  round-headed  and 
flat-headed  borers,  their  leaves  eaten  by  tent-caterpillars,  the 
buds  attacked  by  the  larvse  of  the  bud-moth,  and  the  fruit 
burrowed  into  by  the  codling-moth  grub. 

The  insects  attacking  a  particular  part  of  the  tree,  as  the 
leaves,  may  effect  their  injury  in  different  ways.  They  may 
eat  the  leaves,  as  caterpillars,  beetles  and  other  insects  with 
biting  mouth-parts  do;  or  suck  the  plant  juices  from  them,  as 
the  aphids,  scale-insects  and  other  insects  with  sucking  mouth- 
parts  do.  Similarly  with  the  fruits.  Some  insect  pests  bite 
holes  in  them,  some  suck  juice  from  them,  and  some  bore  un- 
sightly tunnels  in  them,  the  insects  feeding  and  developing  in 
the  very  heart  of  the  fruit. 

Even  in  the  case  of  two  different  insects  that  attack  the  same 
parts  of  the  same  kind  of  orchard  trees  in  much  the  same  way, 
as  with  two  biting  insects  that  eat  the  leaves,  there  may  yet  be 
such  differences  in  their  life  history  and  habits  that  the  best 
remedies  for  them  may  be  radically  different.  The  remedy  for 
one,  which  may  be  a  wingless  insect,  might  be  an  easy  means  of 
preventing  its  access  to  the  leaves;  for  the  other,  a  winged 

421 


422    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

kind,  which  cannot  be  kept  from  the  leaves,  the  remedy  may  be 
the  application  of  a  poison  on  the  leaf  surfaces  so  that  with  each 
bite  will  go  a  dose  of  poison. 

Thus  there  is  not  much  practical  advantage  in  discussing 
in  general  terms  the  insect  pests,  or  the  conditions  of  insect 
attack,  of  orchard  trees.  We  believe  it  will  be  better  worth 
while  for  the  elementary  student  to  try  to  get  acquainted  with 
a  few  of  the  more  important  specific  orchard  pests  in  his 
locality,  and  to  that  end  we  have  given  in  the  following 
paragraphs,  brief  accounts  descriptive  of  the  insect,  its  life, 
the  character  of  the  injury  done  by  it,  and  the  approved  reme- 
dies for  it,  of  a  number  of  the  most  serious  and  widespread  of 
these  pests.  Some  of  these  insects  can  be  found  and  observed 
by  the  student  at  almost  any  time  of  the  year  in  almost  any 
orchard. 

For  fuller  information  about  the  insects  mentioned  in  this 
chapter,  and  for  accounts  of  many  others,  injurious  to  orchards, 
some  manual  of  economic  entomology  may  be  consulted.  San- 
derson's "Insect  Pests  of  Farm,  Garden  and  Orchard"  is  an 
excellent  recent  book  of  this  kind.  O'Kane's  "Injurious 
Insects"  is  another. 

Codling -moth  (Cydia  pomonella). — Of  all  the  pests  of  apples, 
the  codling-moth  is  easily  first  in  importance.  In  many 
orchards  where  the  codling-moth  is  uncontrolled  by  spraying 
50  per  cent,  to  90  per  cent,  or  more  of  the  fruit  is  infested. 
By  proper  spraying  the  amount  of  loss  may  be  reduced  to 
only  5  per  cent,  or  even  2  per  cent,  yet  this  insect  now  costs 
us,  when  we  consider  both  the  loss  from  bad  fruit  and  the 
amount  expended  in  fighting  it,  about  twenty  million  dollars  a 
year. 

The  winter  is  passed  in  the  larval  stage  as  a  little  white 
grub  safely  hidden  away  in  a  tough  little  cocoon  underneath 
the  rough  bark  of  the  tree  or  in  other  protected  places  in  the 
orchard  or  in  the  store  room  where  the  apples  have  been  stored 
for  the  winter.  Early  in  the  spring  the  larva  changes  to  pupa, 
and  about  the  time  the  trees  are  in  bloom  there  issues  the 
small  purplish-brown  moth.  It  has  a  wing  expanse  of  but 
three-fourths  of  an  inch.  The  fore- wings  are  marked  by  fine 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   423 

greenish  lines  or  bands  and  often  by  minute  golden  spots  on 
the  outer  margin.  The  hind  wings  are  grayish,  and  darker 
toward  the  outer  margin.  The  codling-moths  fly  at  dusk  and 
usually  lay  their  eggs  on  the  leaves.  The  larvae  may  feed  on 
the  tender  leaves  for  a  short  time,  but  they  soon  make  their 
way  to  the  calyx,  or  blossom,  end  of  the  forming  fruit  and  enter 
there.  A  few  may  enter  at  the  stem  end  or  in  the  sides  of 
the  fruit.  For  the  next  three  or  four  weeks  they  burrow 
and  feed  in  the  apple,  usually  around  the  core,  and,  finally, 
having  attained  their  full  growth,  bore  their  way  out  and  drop 


FIG.  196. — Codling-moth,  Cydia  pomonella.     (Twice  natural  size.) 

to  the  ground  and  hide  themselves  under  pieces  of  rough  bark 
or  other  rubbish  where  they  form  a  thin  cocoon.  In  some 
regions  there  is  only  a  single  generation  each  year,  but  in 
most  regions  there  are  two  and  in  some  places  three  and  even 
part  of  a  fourth. 

If  all  the  larvae  that  hide  themselves  away  in  the  fall  were  to 
live  through  the  winter  the  insect  would  be  a  much  more  serious 
pest  than  it  is.  Fortunately  a  large  proportion  of  them  is 
destroyed  by  the  birds  during  the  winter.  Many  apples  are 
carried  into  the  store  houses  before  the  worms  have  issued 
from  them,  and  when  these  leave  the  apples  they  hide  away 
in  protected  places,  and  the  moths  that  issue  the  next  spring 
will  fly  back  to  the  orchards  unless  the  store  rooms  are  care- 
fully screened  so  that  they  cannot  escape.  In  many  places 


424    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

it  has  been  found  worth  while  to  tie  bands  of  burlap  around 
the  tree  so  that  the  larvae  will  find  there  suitable  places  to 
pupate.  During  the  summer  these  bands  are  examined  often 


FIG.    197. — The  larva,    or    worm,    of    codling-moth,   Cydia    pomonella. 
(Three  times  natural  size;  after  Slingerland.) 

and  any  larvae  or  pupae  found  are  destroyed.  In  the  fall  they 
should  be  removed  or  very  carefully  examined  to  see  that  none 
of  the  larvae  pass  the  winter  in  them. 


FIG.  198. — Cocoons  of  codling-moth  larvae  under  bark  on  old  apple 
tree.  An  empty  pupa  case  shows  where  the  moth  has  issued  from  one  of 
the  cocoons.  (Natural  size.) 

Spraying  with  Paris  green  or  arsenate  of  lead  must  be  relied 
upon  as  the  principal  means  for  controlling  this  pest.  Three 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   425 

or  four  pounds  of  arsenate  of  lead  (paste)  to  one  hundred  gallons 
of  water  make  the  most  effective  spray.  The  proper  time  to 
spray  for  this  pest  is  just  after  the  petals  fall  and  while  the 
calyx  cup  is  still  open.  It  is  of  prime  importance  that  the 
calyx  cup  of  every  small  apple  or  pear  be  filled  in  order  that 
the  first  meal  that  the  young  larva  takes  on  the  fruit  will 
contain  enough  of  the  poison  to  destroy  it.  In  regions  where 
most  of  the  larvae  of  the  first  brood  hatch  at  about  the  same 
time  it  has  been  found  that  a  single  spraying  thoroughly  done 
at  the  proper  time  will  save  95  or  sometimes  98  per  cent,  of  the 
fruit.  In  places  where  the  larvae  issue  irregularly  it  may  be 
desirable  to  give  a  second  spraying  about  three  or  four  weeks 
after  the  blossoms  fall,  or  even  a  third  still  later.  The  first 
spraying  should  be  done  by  using  a  coarse  spray  with  a  pressure 
of  from  150  to  250  pounds.  This  drives  the  spray  through  the 
stamens  and  into  the  lower  calyx  cavity.  Later  sprayings 
may  be  applied  as  a  finer  mist  in  order  that  a  thin  film  of  the 
poison  may  be  left  over  the  surface  of  the  fruit  and  leaves. 

The  Apple-maggot,  or  Railroad-worm  (Rhagoletis  pomonella). 
— Sometimes  an  apple  that  is  apparently  perfectly  sound  ex- 
ternally will  be  found  to  be  "railroaded"  inside  by  a  dozen 
or  more  little  maggots  that  make  discolored  streaks  through- 
out it.  When  these  larvae  leave  the  apples  they  pupate  in  the 
ground  or  in  the  boxes  or  barrels  where  the  apples  have  been 
stored,  and  early  the  next  summer  the  adult  flies  issue.  They 
are  a  little  smaller  than  the  house-fly,  and  have  the  wings  con- 
spicuously marked  by  four  black  connected  bands;  the  body  is 
blackish  with  yellowish  head  and  legs,  and 'with  narrow  white 
stripes  across  the  abdomen. 

This  pest  can  be  controlled  by  destroying  infested  summer 
apples  by  gathering  them  up  at  least  twice  a  week,  or  by  allow- 
ing hogs  to  run  in  the  orchard  and  eat  all  the  apples  that  fall. 

The  Cherry  Fruit-fly  (Rhagoletis  cingulata) . — This  insect,  the 
larvae  of  which  are  often  found  in  cherries,  looks  very  much 
like  the  adult  of  the  apple-maggot,  but  it  is  somewhat  smaller 
and  the  black  bands  across  the  wings  are  arranged  differently. 

All  fruit  found  to  be  affected  should  be  destroyed  before  the 
larvae  have  a  chance  to  escape  and  pupate. 


426    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  Mediterranean  Fruit-fly  (Ceratitis  capitata). — This  is 
probably  the  most  important  fruit  pest  in  the  world.  At  the 
time  this  is  being  written  it  does  not  yet  occur  in  North  America, 
but  there  is  always  danger  of  its  being  introduced  from  Hawaii 
or  other  tropical  islands  where  it  is  now  doing  much  damage. 
Under  favorable  conditions  it  multiplies  very  rapidly  and  as 
it  attacks  many  kinds  of  cultivated  and  wild  fruits  its 
introduction  into  this  country  might  result  disastrously  to 
much  of  our  fruit,  particularly  on  the  Pacific  Coast  and  in  the 


FIG.  199. — Mediterranean  fruit-fly,  Ceratitis  capitata.     (Much  enlarged.) 

South.  The  fly  is  a  little  smaller  than  the  common  house- 
fly and  is  closely  related  to  the  two  fruit-flies  just  described. 
Figure  199  shows  the  characteristic  markings  of  the  wings. 
The  quarantine  officers  in  all  of  our  ports  are  carefully  watch- 
ing for  this  pest,  and  are  destroying  all  fruit  or  vegetables  that 
may  contain  the  living  larvae. 

The  Plum  Curculio  (Conotrachelus  nenuphar). — While  this 
little  insect  causes  most  injury  to  plums  it  may  also  attack 
peaches  and  cherries.  The  adult  is  a  thick-set  beetle  a 
little  more  than  three-eighths  of  an  inch  long,  black,  but  covered 
with  short,  fine,  brownish  hairs;  there  are  also  a  few  patches 
of  white  hairs.  The  back  is  marked  w'ith  conspicuous  ridges 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   427 

and  tubercles.  The  head  is  produced  into  a  long  snout.  The 
female  beetle  hibernates  under  leaves  or  rubbish,  and  as  soon 
as  the  fruit  is  formed  commences  to  lay  her  eggs  in  it  in  small 
holes  that  she  makes  with  her  snout.  After  laying  her  eggs 
she  makes  a  small  crescent-shaped  cut  in  the  skin  of  the  fruit. 
This  characteristic  mark  has  suggested  the  common  name 
"little  Turk"  for  this  pest.  The  larvae  usually  feed  around 
the  pit,  often  causing  the  fruit  to  drop.  When  full  grown  they 
crawl  out,  pupate  in  the  ground,  and  the  adult  beetles,  which 
issue  three  or  four  weeks  later,  feed  on  the  ripening  fruit,  often 
doing  much  damage  before  they 
seek  out  a  suitable  hiding  place 
in  which  to  pass  the  winter. 

As  the  beetles  have  the  habit 
of  "playing  possum"  when 
alarmed  many  of  them  may  be 
caught  by  jarring  the  tree  with  a 
padded  club  and  causing  them  to  FlG-  200. — The  plum  cur- 
Hrnn  tr>  a  ranvac  that  hac  KPPTI  culio>  Conolrachelus  nenuphar. 

drop  to  a  canvas  that  nas  been    (Enlarged.  after  siingerland.) 
spread    under    the    tree.     Some 

fruit  growers  use  curculio  catchers  made  by  stretching  a 
canvas  on  a  frame  that  is  mounted  on  wheels,  a  slit  being 
left  in  one  side  to  allow  the  apparatus  to  be  wheeled  against 
the  trunks  of  the  trees.  Recent  experiments  seem  to  indicate 
that  spraying  the  leaves  with  arsenate  of  lead  may  be  a  satis- 
factory method  of  control  as  the  beetles  feed  for  awhile  on  the 
foliage  when  they  first  issue  in  the  spring. 

Tent -caterpillars  (Malacosoma  americana). — The  larva?  of 
many  moths  often  occur  in  such  numbers  in  the  orchard  that 
they  quite  strip  the  trees  of  their  foliage.  Among  the  most 
conspicuous  of  this  group  of  pests  are  the  tent-caterpillars, 
so-called  on  account  of  their  habit  of  living  together  in  colonies 
and  spinning  a  large  web  or  tent  in  which  or  on  which  they 
rest  at  night  or  at  other  times  when  not  feeding.  When  full 
grown  each  finds  a  convenient  place  to  spin  a  thin,  tough,  white 
cocoon  from  which,  a  few  weeks  later,  the  adult  moth  issues 
and  lays  the  eggs  which  are  to  remain  on  the  trees  over  winter. 
The  eggs  are  laid  in  a  mass  usually  on  the  smaller  branches, 


428    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


often  making  a  complete  band  around  a  twig.  They  are 
covered  with  a  frothy,  glue-like  substance  which  protects  them 
during  the  winter  and  furnishes  the  first  meals  for  the  young 
larvae. 

These  pests  have  many  natural  enemies,  such  as  birds, 
Hymenopterous  parasites  and  an  important  bacterial  disease. 
These  help  much  to  control  them,  but  it  is  sometimes  necessary 


FIG.  201. — Egg  mass  and  small  tent  of  tent-caterpillar, 
thirds  natural  size.) 


(About  two- 


to  resort  to  active  methods  of  control.  The  eggs  may  be 
pruned  off  in  the  winter  and  placed  in  a  box  covered  with  a 
screen  so  that  the  parasites  may  be  allowed  to  escape  and  the 
larvae  be  retained  when  they  hatch.  The  tents  containing 
the  young  larvae  can  be  quickly  gathered  and  destroyed  when 
they  are  small.  Spraying  very  early,  before  the  blossoms  ap- 
pear, with  arsenate  of  lead  will  kill  many  of  the  larvae. 

Canker-worms. — -The  canker-worms,    inch-worms,  measur- 
ing-worms, or  loopers  are  common  throughout  nearly  all  parts 


of  the  United  States.     There  are  two  species,  the  spring  canker- 
worm,  Paleacrita  vernata,  which  has  only  one  pair  of  abdominal 


FIG.  202. — A  trio  of  apple  tent-caterpillars,  larvae  of  the  moth  Mala- 
cosoma  americana.  These  caterpillars  make  the  large  unsightly  webs  or 
tents  in  the  apple  trees,  a  colony  of  the  caterpillars  living  in  each  tent. 
(Natural  size;  after  Slingerland.) 

legs,  and  the  fall  canker-worm,  Alsophila   pometaria,   which 
has  two  pairs.     Otherwise  they  are  very  similar  in  appearance. 


430    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

They  have  similar  habits  also,  except  that  the  adult  of  the 
spring  canker-worm  lays  her  eggs  early  in  the  spring,  while  the 
moth  of  the  fall  canker-worm  lays  hers  late  in  the  fall.  The 
larvae  of  both  species  issue  about  the  same  time  in  the  spring 
and  feed  on  the  tender  foliage.  The  young  canker-worms 
have  a  habit  of  dropping  from  the  tree  when  it  is  jarred  or 
shaken  and  hanging  suspended  by  a  slender  thread  which  they 


FIG.  203. — California  tussock-moth,  Hemerocampa  vetusta;  larva  and  co- 
coon with  an  egg  mass  on  the  cocoon.     (About  natural  size.) 

spin  from  the  mouth  as  they  drop.  They  pupate  in  the  ground 
and  the  spring  canker-worm  passes  the  winter  in  this  stage, 
the  adult  issuing  early  in  the  spring.  The  female  moth  is 
entirely  wingless  and  less  than  one-half  of  an  inch  long.  They 
climb  up  the  trunks  of  the  trees  and  lay  their  eggs  in  irregular 
masses  underneath  the  loose  bark  or  in  cracks  or  crevices.  The 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   431 

fall  canker-worm  moths  issue  during  November  and  December 
and  lay  the  eggs  which  are  to  hatch  early  the  next  spring. 

The  most  efficient  remedy  is  to  spray  with  arsenate  of  lead 
as  soon  as  the  foliage  is  well  open.  A  second  later  spraying  is 
sometimes  desirable.  It  is  a  common  practice  to  place  bands 
around  the  trees  to  prevent  the  females  crawling  up  to  lay  their 
eggs.  These  bands  usually  consist  of  a  strip  of  some  heavy 
paper  tied  tightly  around  the  tree  after  the  bark  has  been  made 
smooth.  It  is  then  covered  with  some  sticky  substance,  such 
as  "tanglefoot,"  which  will  prevent  the  moths  from  crawling 
over  it. 

The  White-marked  Tussock-moth  (Hemerocampa  leuco- 
stigma). — The  females  of  the  tussock-moths  are  similar  in 


FIG.  204. — California  tussock-moth,  Hemerocampa   vetusta;  male  above; 
wingless  female  below.     (Natural  size.) 

appearance  to  the  female  canker-worm  moths,  being  entirely 
without  wings.  When  they  issue  from  the  cocoon  they  seldom 
travel  far,  often  simply  crawling  on  top  of  the  cocoon  to  deposit 
their  eggs.  The  larvae  vary  a  great  deal  in  color  and  markings, 
but  they  are  always  covered  with  long  blackish  or  yellowish 
hairs  and  have  conspicuous  tufts  toward  the  anterior  and 
posterior  ends  of  the  body.  On  the  Pacific  Coast  the  most 
common  tussock-moth  is  H.  zetusta,  but  there  are  other  species 
that  may  be  found  in  the  orchard  or  in  woodland  trees. 


432    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  best  method  of  control  is  to  gather  the  eggs  during  the 
winter  and  destroy  them.  The  larvae  seem  to  be  very  resistant 
to  poisons,  and  when  the  arsenical  sprays  are  used  it  is  necessary 
to  make  them  very  strong. 

Climbing  Cut-worms. — Several  species  of  smooth-bodied 
cut-worms  often  climb  the  trees,  eating  the  foliage  or  destroying 
the  young  fruit.  Sometimes  these  cut-worms  go  in  great 


FIG.  205. — Green-fruit  worms,  Xylina  grotei,  at  left,  and  Xylina  anten- 
nata,  at  right.     (Natural  size;  after  Slingerland.) 


bands  or  armies  traveling  across  the  country  and  destroying  all 
the  vegetation  in  their  path.  The  adults,  which  are  moths  that 
usually  fly  only  at  night,  are  mostly  grayish  or  brownish,  and 
are  often  called  owlet-moths  on  account  of  the  peculiar  appear- 
ance of  the  eyes  and  head. 

About  the  only  successful  method  of  combating  cut-worms 
after  they  have  once  gained  foothold  on  the  trees  is  to  jar 
them  off  and  destroy  them.  Fortunately  they  are  attacked  by 
several  natural  enemies  which  generally  keep  them  in  control. 

The  Bud -moth  (Tmetocera  ocellana). — Often  the  unfolding 
leaves  of  fruit  trees  are  tied  together  with  silken  webs  making 


INSECTS  INJURIOUS  TO  ORCHARD  TREES    433 

an  irregular  nest  in  which  the  larvae  of  the  bud-moth  feed  and 
in  which  they  pupate.  Because  they  attack  the  buds  before 
they  are  open  they  are  able  to  do  considerable  damage  before 
anything  can  be  done  to  control  them. 

A  careful  spraying  with  arsenate  of  lead  just  as  the  leaves 
begin  to  unfold  is  about  the  only  remedy  that  can  be  recom- 
mended. 

^  The  Pear  Thrips  (Euthrips  pyri).—For  several  years  this 
little  insect  has  been  the  most  serious  pest  with  which  the 
orchardists  of  central  California  have  had  to  contend,  and 
recently  it  has  been  discovered 
that  it  also  occurs  in  some  of 
the  eastern  states  where  it  does 
considerable  damage.  It  at- 
tacks many  kinds  of  orchard 
trees,  but  does  particular  injury 
to  pears,  cherries  and  prunes. 
The  adult  thrips  are  minute, 
black-bodied  insects  with  their 
four  long  narrow  wings  fringed 
with  long  hairs.  They  appear 
early  in  the  spring  and  soon 
make  their  way  into  the  ten- 
derest  part  of  the  bud,  often 
completely  destroying  it.  A 
little  later  they  begin  laying  the  eggs  from  which  the  wingless 
young  thrips  hatch.  These  continue  the  destructive  work 
begun  by  the  adults.  The  insect  passes  the  winter  in  the 
larval  and  pupal  stages  in  the  ground,  the  adult  issuing  very 
early  the  following  spring. 

In  fighting  this  pest  some  insecticide  must  be  used  that  will 
penetrate  the  buds  and  kill  the  thrips  without  injuring  the 
buds.  The  distillate  oil  emulsion  and  tobacco  extract  (see 
page  417)  have  proved  most  efficient  in  California.  The  first 
spraying  must  be  done  as  soon  as  the  adult  thrips  are  numerous 
on  the  trees,  the  second  application  should  follow  ten  days 
later,  and  still  a  third,  which  is  for  the  larvae,  should  be  given 
about  two  weeks  after  the  second.  Deep  plowing  in  the  fall 


FIG.  206. — The  pear  thrips,  adult- 
(Much  enlarged;  after  Moulton.) 


434    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  winter  will  destroy  many  of  the  larvae  and  pupae  that  are 
in  the  ground. 

The  Pear- leaf  Blister-mite  (Eriophyes  pyri}. — This  little 
mite,  that  causes  red  blister-like  blotches  on  the  leaves  of  the 
pears  and  sometimes  of  the  apples,  is  not  an  insect,  as  is 
commonly  supposed,  but  is  an  Arachnid  and  is  discussed  on 
page  213. 

The  Peach  Borer  (Sanninoidea  exitiosa). — This  insect  is 
probably  the  most  important  of  those  that  attack  the  trunk 
of  orchard  trees.  Not  only  the  peach  but  the  apricot,  plum, 


FIG.  207. — California  peach-tree  borer,  larva  of  Sanninoidea  opalescens, 
in  cocoon.     (About  natural  size.) 

prune  and  nectarine  may  be  seriously  affected  by  it.  The  eggs 
are  laid  on  the  outer  bark  near  the  base  of  the  trunk.  The 
larvae  burrow  in  and  feed  on  the  inner  bark  usually  close  to  the 
surface  of  the  ground.  Their  presence  is  indicated  by  gummy 
exudations  mixed  with  the  castings  of  the  larvae.  Several 
larvae  feeding  on  a  tree  may  completely  girdle  it  or  so  weaken 
it  that  it  will  bear  little  fruit  and  be  much  more  subject  to 
the  attacks  of  other  insects  or  diseases.  Much  of  the  sawdust- 
like  castings  and  bits  of  bark  are  incorporated  in  the  cocoon 
which  the  larva  spins  in  the  end  of  the  burrow  or  on  the  surface 
of  the  tree,  or  in  the  ground  close  to  the  surface.  The  adult 


INSECTS  INJURIOUS  TO  ORCHARD  TREES     435 

insects  are  beautiful,  clear-winged,  steel-blue  moths.  The 
abdomen  of  the  female  is  marked  by  a  conspicuous  orange  band, 
that  of  the  male  by  three  or  four  much  narrower  stripes. 

The  moths  may  sometimes  be  kept  from  laying  their  eggs 
on  the  tree  if  the  trunk  is  wrapped  with  some  heavy  paper 
and  the  earth  mounded  up  around  the  crown.  Various  re- 
pellent or  protective  washes  have  been  tried  with  but  little 
success.  After  the  larvae  have  entered  the  tree  they  must  be 
dug  out  and  destroyed.  If  the  trees  are  well  mounded  up 


FIG.  208. — Adults,  male  and  female,  California  peach-tree  borer,  Sanni- 
noidea  opalescens.     (About  natural  size.) 

early  in  the  spring  it  will  greatly  facilitate  the  work  of  "  worm- 
ing" early  in  the  fall,  for  most  of  the  young  larvae  will  be  above, 
the  surface  of  the  ground  when  the  mounds  are  levelled. 

A  closely  related  species  known  as  the  California  peach-tree 
borer,  S.  opalescens,  occurring  on  the  Pacific  Coast,  has  habits 
and  a  life  history  similar  to  the  eastern  species  and  yields  to 
the  same  methods  of  control. 

The  Peach  Twig-borer  (Anarsia  lineatella). — Early  in  the 
spring  many  of  the  tender  shoots  on  the  peach  trees  will  often 


436    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

wither  and  die.  If  these  are  examined,  minute,  brownish, 
black-headed  larvae  may  be  found  in  them.  These  larvae  bore 
down  the  center  of  the  stem  for  one  or  two  inches.  When  the 
firmer  wood  is  reached  they  leave  the  dead  shoot  and  attack 
another  live  one;  thus  one  larva  may  destroy  several  twigs. 
When  full  grown  the  larvae  crawl  down  the  branches  to  the 
trunk  of  the  tree,  where  they  pupate.  The  small  dark  gray 
moths  that  issue  from  these  pupae  lay  their  eggs  on  the  new 
twigs  near  the  bases  of  the  leaves.  These  eggs  soon  produce 
the  second  generation  of  larvae  which  feed  on  the  twigs  as  did 
the  first  generation.  In  some  places  a  third  brood  of  larvae 
may  appear  late  in  the  fall.  These,  as  well  as  the  members 
of  the  second  brood,  will  often  attack  the  fruit,  usually  working 
in  or  around  the  seed,  often  doing  much  damage  and  always 
making  the  fruit  unattractive. 

The  larvae  of  the  last  brood  pupate  early  in  the  fall,  and  the 
moths  that  issue  from  these  pupae  lay  their  eggs  close  to  the 
crotches  of  the  tree.  The  young  larvae  that  issue  from  these 
eggs  bore  into  the  bark  in  the  crotches  and  make  a  little  cell 
in  which  they  pass  the  winter.  Little  turrets  made  of  pellets 
woven  together  with  silk  spun  by  the  larvae  mark  the  locations 
of  these  silk-lined  cells  in  which  the  larvae  hibernate.  As 
soon  as  the  buds  begin  to  grow  in  the  spring  the  larvae  leave 
their  burrows  and  begin  their  destructive  work.  The  most 
effective  remedy  is  to  spray  the  trees  with  sulphur-lime  as 
soon  as  the  buds  begin  to  swell.  This  will  kill  the  larvae 
after  they  have  opened  up  the  winter  cells  and  are  migrating 
from  these  to  the  tender  shoots. 

The  Round-headed  Apple-tree  Borer  (Saperda  Candida}. — 
Frequently  the  trees  in  young  apple  orchards  are  injured  by 
cylindrical  round-headed  larvae  boring  in  the  trunk.  A  few 
of  these  larvae  working  in  a  small  tree  may  entirely  girdle  it. 
After  feeding  in  the  cambium  for  twro  seasons  the  larvae  bore 
into  the  heart  of  the  wood,  and  not  until  the  third  season  do 
they  change  to  the  pupae  from  which  the  adult  beetles  issue. 

The  methods  of  control  are  much  the  same  as  those  suggested 
for  the  peach  borer,  the  object  being  to  keep  the  beetle  from 
laying  her  eggs  on  the  tree,  and  to  cut  out  any  larvae  that  may 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   437 

have  gained  an  entrance  before  they  have  had  time  to  do 
much  injury.  A  heavy  coating  of  whitewash  kept  over  the 
trunk  of  the  trees  during  the  summer  affords  much  protection. 

There  is  also  a  flat-headed  borer  that  works  in  the  trees 
in  much  the  same  way,  and  can  be  controlled  by  the  same 
methods. 

The  Periodical  Cicada  (Cicada  septemdecim) . — It  is  com- 
monly supposed  that  cicadas  do  much  damage  to  the  orchard 
trees.  As  a  matter  of  fact,  however,  the  injury  that  they  cause 
is  not  particularly  serious  except  to  young  trees.  When  the 
female  is  laying  her  eggs  she  makes  rather  large  holes  or  wounds 
in  the  bark  with  her  ovipositor.  As  soon  as  the  young  hatch 
they  drop  to  the  ground  and  bury  themselves  in  the  soil 
where  they  feed  on  roots  and  other  substances  for  more  than 
sixteen  years,  finally  changing  to  the  pupae  or  nymphs.  Then, 
seventeen  years  after  the  eggs  have  been  laid,  they  issue 
as  the  adult  cicadas,  which  soon  lay  their  eggs  and  die.  As 
there  may  be  more  than  one  brood  in  a  locality  with  different 
times  of  emergence  it  is  not  always  seventeen  years  between 
the  outbreaks.  Government  bulletins  giving  dates  upon  which 
all  the  various  broods  occurring  in  the  United  States  may  be 
expected  to  issue,  can  be  obtained  by  making  application  as 
suggested  on  page  420. 

There  are  other  species  of  cicadas  that  complete  their 
development  in  much  less  time.  Although  these  insects  do 
not  at  all  resemble  grasshoppers,  the  two  have  been  confused 
under  the  term  locust,  the  periodical  cicada  often  being  re- 
ferred to  as  the  seventeen-year  locust;  the  term  locust,  how- 
ever, is  properly  applied  only  to  the  grasshoppers. 

APHIDS,  OR  PLANT-LICE 

In  structure  and  habits  the  plant-lice  (family  Aphidida) 
are  among  the  most  interesting  of  our  insects.  They  are  all 
very  small  and  soft-bodied,  and  feed  upon  the  leaves  or  stems 
of  plants,  sucking  the  sap  by  means  of  a  long  slender  beak. 
Their  life  history  is  subject  to  considerable  variation  among 
the  different  species,  but  they  all  agree  in  certain  features. 


438    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  eggs  are  usually  laid  in  the  fall  on  the  twigs  or  other  parts 
of  the  plant  on  which  the  insect  is  feeding.  These  eggs  go  over 
the  winter.  The  young  aphids  that  hatch  from  these  eggs  in 
the  spring  immediately  begin  feeding  upon  the  host  plant. 
Usually  this  is  a  generation  of  females.  When  about  two 
weeks  old  they  begin  giving  birth  to  living  young  which  in  turn 
give  birth  to  other  young  and  so  through  the  summer.  Thus 
there  is  a  series  of  generations  of  wingless  females  that  give 
birth  parthenogenetically  to  living  young.  In  the  fall  there 
appears  a  generation  that  is  composed  of  both  males  and 
females  which  are  usually  winged.  After  mating,  the  females 
lay  the  winter  eggs.  At  any  time  during  the  summer  when  food 
becomes  scarce  or  when  conditions  are  otherwise  unfavorable, 
there  may  appear  winged  generations  of  females  that  fly  to 
other  plants  and  thus  provide  for  the  distribution  of  the  species. 
This  method  of  reproduction  and  distribution  makes  possible 
a  very  rapid  increase  of  the  number  of  individuals.  The  off- 
spring from  a  single  female,  if  all  the  members  of  the  summer 
generations  lived,  would  amount  to  hundreds  of  millions. 
Fortunately,  they  do  not  all  live.  They  have  many  natural 
enemies,  chief  among  which  are  the  ladybird-beetles,  the 
syrphus-fly  larvae,  the  lace-wing-fly  larvae,  the  braconid-flies, 
etc. 

Certain  secretions  from  the  body  of  the  aphids  play  an 
important  part  in  their  life.  Through  small  pores  or  openings 
scattered  over  the  body,  many  kinds,  as  the  woolly  aphis  and 
others  like  it,  secrete  a  waxy  substance  that  forms  a  mat  of 
felted  or  woolly  threads  which  afford  the  insects  considerable 
protection.  Nearly  all  of  the  aphids  also  secrete  a  sweet, 
sticky  substance  known  as  honey-dew.  Formerly  it  was  sup- 
posed that  this  honey-dew  came  from  the  two  little  tubercles 
that  occur  on  the  posterior  end  of  the  body  of  many  of  them, 
but  it  is  now  known  that  it  issues  in  drops  from  the  alimentary 
canal.  Sometimes  so  much  is  produced  that  the  plants  and 
the  ground  below  are  quite  covered  with  the  sticky,  honey-like 
secretion.  Many  insects  are  very  fond  of  this  honey-dew, 
the  ants  being  especially  partial  to  it.  On  page  492  is  given 
an  account  of  a  particular  way  in  which  the  ants  care  forcer- 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   439 

tain  aphids  for  the  sake  of  their  honey-dew.  But  the  ants  do 
not  always  assume  such  a  definite  relation  to  the  welfare  of 
the  aphids.  Usually  they  appear  on  aphis-infested  trees  only 
to  feed  on  the  honey-dew,  and  neither  injure  nor  care  for  the 
aphids.  The  black  sooty  fungus  that  grows  on  this  honey-dew 
often  completely  covers  the  leaves  and  fruit  making  them  very 
dirty  and  disagreeable  to  the  sight  and  touch. 

The  Green  Apple  Aphis  (Aphis  pomi.} — This  is  one  of  the 
most  common  aphids  found  on  apple  trees.  It  feeds  on  the 
tender  tips  of  the  green  shoots  and  upon  the  young  leaves, 
causing  the  leaves  to  become  twisted  and  curled  in  such  a 
way  that  they  afford  excellent  protection  for  the  aphids  that 
are  feeding  within.  At  any  time  during  the  summer  winged 
females  may  appear  and  fly  to  other  trees.  Early  in  the  fall 
the  sexual  generation  appears  and  the  females  lay  their  eggs 
on  the  apple  twigs.  During  the  winter  time  these  small,  shin- 
ing black,  oval  eggs  may  be  found  on  the  twigs,  usually  near  the 
tips.  The  best  method  of  control  is  to  prune  off  and  destroy 
all  of  the  twigs  on  which  the  eggs  are  found.  A  strong  sulphur- 
lime  spray  will  kill  many  of  the  eggs,  but  it  does  not  always 
give  entire  satisfaction.  As  the  leaves  begin  to  curl  soon  after 
the  aphids  attack  them  it  is  hard  to  reach  them  with  any  spray. 
A  good  strong  tobacco  spray,  however,  will  kill  many  of  them 
if  it  is  used  very  early.  Kerosene  emulsion  may  also  be  used. 
It  is  necessary  to  use  considerable  force  with  any  spray  for 
these  insects  in  order  to  drive  it  into  the  curled  leaves. 

The  Rosy  Apple  Aphis  (Aphis  sorbi}. — This  species  resembles 
the  preceding  in  habits  and  general  appearance,  but  the  body 
is  usually  rosy  in  color.  The  color  may  vary,  however,  from 
grayish  to  purplish  or  black.  The  winter  eggs  are  not  as 
conspicuous  as  the  eggs  of  the  green  aphis,  and  are  not  easily 
detected.  It  is  necessary  therefore  to  rely  upon  the  efficiency 
of  the  sulphur-lime  wash  for  destroying  the  winter  eggs,  or 
upon  some  of  the  contact  sprays  for  killing  the  insects  after 
they  have  attacked  the  leaves.  It  is  thought  that  one  genera- 
tion of  these  aphids  leaves  the  apple  and  migrates  to  some  un- 
known food  plant  on  which  they  may  pass  the  principal  part 
of  the  summer.  In  the  fall  some  of  the  winged  females  return 


440    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

to  the  apple  trees  and  give  rise  to  the  sexual  generation  which 
produces  the  winter  eggs. 

The  Woolly  Apple  Aphis  (Sckizoneura  'lanigera). — -This  is 
the  most  destructive  of  the  apple  aphids,  doing  particular 
damage  in  young  orchards,  and  as  its  most  injurious  work 
is  on  the  roots  of  the  trees  its  presence  is  often  not  suspected 
until  the  trees  have  been  badly  damaged.  These  aphids 
secrete  a  white,  woolly,  waxen  substance  that  covers  the  body, 
and  when  a  number  of  them  are  feeding  together  the  white 


FIG.  209. — Apple  leaves  curled  by  rosy  aphis,  Aphis  sorbi.     (Reduced.) 


patches  that  they  make  are  quite  conspicuous.  The  forms  that 
feed  above  ground  usually  attack  the  new  shoots  or  the  tender 
bark  about  wounds  or  scars  on  the  trees.  The  greatest  damage, 
however,  is  done  by  the  root-feeding  forms.  These  gather  in 
small  colonies  over  the  smaller  roots,  where  their  feeding  causes 
knots  or  galls.  If  they  are  abundant  many  of  the  smaller 
rootlets  are  killed  and  young  trees,  particularly,  are  thus  seri- 
ously injured.  The  larger  roots  may  become  very  knotty  and 
much  deformed,  but  the  aphids  are  usually  found  on  the 
smaller  tenderer  roots.  Many  of  the  wingless  aphids  live  over 


INSECTS  INJURIOUS  TO  ORCHARD  TREES    441 

the  winter  on  the  roots  of  the  tree.  Early  in  the  spring 
some  of  these  migrate  to  the  trunks  or  branches,  where  they 
feed  during  the  summer.  There  are  several  generations 
of  apterous  females  during  the  summer.  In  the  fall  winged 
females  appear  which,  it  is  believed  by  some  students,  migrate 
to  elm  trees,  where  the  eggs  are  laid  in  crevices  in  the  bark. 
These  hatch  early  in  the  spring  and  cause  the  curly  leaves  on 
the  elm.  A  little  later  a  generation  containing  winged  females 


FIG.  210. — Woolly  aphis,  Schizoneura  lanigera,  and  the  galls  caused  by 
their  attacks  on  apple  tree  roots.     (Two-thirds  natural  size.) 

appears,  and  some  of  these  migrate  back  to  apple  trees  and  start 
new  colonies  there.  Elm  trees  near  an  orchard  may  thus  serve 
as  a  source  of  infection.  It  would  probably  be  much  easier 
to  keep  nursery  trees  free  from  woolly  aphis  if  the  nurseries 
were  not  located  near  groves  of  elms. 

The  aphids  that  occur  on  the  trunk  and  branches  may  be 
killed  by  spraying  with  kerosene  emulsion,  whale  oil  soap, 
tobacco  extract  or  other  contact  sprays.  It  is  necessary  that 


442    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

the  spray  be  applied  with  much  force  in  order  that  it  may 
penetrate  the  woolly  secretion  that  covers  the  insects.  The 
root  forms  are  harder  to  control,  as  it  is  difficult  to  reach  them. 
But  if  the  earth  is  removed  from  all  of  the  roots  that  are  within 
eight  or  ten  inches  of  the  surface,  and  those  affected  then 
treated  with  kerosene  emulsion  or  tobacco  extract,  most  of 
the  aphids  may  be  destroyed.  If  the  ground  is  thoroughly 
wet  with  the  emulsion  or  tobacco  it  seems  to  act  as  a  repellant 
and  the  roots  may  not  be  infested  again  for  some  time.  As  it 
is  the  young  trees  that  suffer  most  from  the  attacks  of  this 
insect,  great  care  should  be  taken  to  see  that  the  pest  is 
not  introduced  into  the  orchard  with  nursery  stock.  No 
nursery  stock  that  shows  any  indication  of  having  been  at- 
tacked by  this  aphis  should  be  accepted,  for  by  no  treatment 
can  it  be  made  absolutely  safe.  Nursery  men  often  sprinkle 
tobacco  dust  on  the  ground  along  the  rows  of  growing  young 
trees.  This  not  only  kills  some  of  the  aphids  that  are  close 
to  the  surface,  but  it  acts  as  a  repellant,  for  a  while  at  least. 
Trees  grown  on  Northern  Spy  stock  do  not  seem  to  be  as 
seriously  attacked  as  those  grown  on  other  roots. 

Black  Peach  Aphis  (Aphis  persiccz-niger.} — There  are 
several  other  species  of  aphids  that  attack  the  peach,  plum  and 
other  orchard  trees,  usually  confining  their  attacks  to  the 
foliage  or  tender  twigs.  The  black  peach  aphis  is  of  particular 
importance  because,  like  the  woolly  aphis  of  the  apple,  it  attacks 
the  roots  as  well  as  the  leaves  and  branches.  Both  the  winged 
and  the  wingless  aphids  may  be  found  on  the  foliage  during 
the  summer,  but  winged  forms  do  not  seem  to  occur  on  the 
roots.  The  aphids  may  be  found  on  any  of  the  roots  through- 
out the  year,  but  they  do  most  damage  to  the  smaller  roots. 
As  they  cling  tenaciously  to  the  roots  they  are  very  apt  to  be 
distributed  on  nursery  stock,  and  great  care  should  be  taken  to 
keep  them  from  being  introduced  into  the  orchard  in  this  way. 
The  colonies  are  established  on  the  foilage  in  the  spring  by  some 
of  the  larvae  migrating  from  the  roots.  The  methods  suggested 
for  controlling  the  woolly  aphis  should  be  used  in  fighting  this 
species. 


INSECTS  INJURIOUS  TO  ORCHARD  TREES  443 

SCALE-INSECTS 

Although  most  of  the  Coccidtz,  or  scale-insects,  are  so  small 
or  obscure  that  they  are  usually  overlooked  by  the  ordinary 
observer  they  are  economically  the  most  important  group  in 
all  the  insect  class.  The  scale-insects  attack  almost  all  kinds  of 
trees  and  shrubs,  but  it  is  difficult  to  make  anything  like  a  reason- 
ably accurate  estimate  of  the  amount  of  damage  done  by  them 
because  so  many  factors  are  involved.  Some  trees  may  harbor 
many  scale-insects  and  yet  show  but  little  injury,  others  when 
only  slightly  infested  by  certain  species  suffer  severely.  The 
injury  may  be  only  temporary,  causing  the  leaves  or  fruit 
to  drop,  or  it  may  be  permanent,  retarding,  dwarfing  or  even 
killing  the  tree.  In  discussing  the  development  and  life  history 
of  the  scale-insects  it  will  be  convenient  to  group  them  into 
three  more  or  less  well-defined  groups.  The  first  group  includes 
the  mealy-bugs,  which  are  common  in  almost  all  greenhouses, 
and  a  few  others,  most  of  which  move  about  over  the  plant 
freely  until  ready  to  lay  their  eggs.  In  these  the  segmentation 
of  the  body  remains  distinct,  and  the  legs  and  antennae  are  func- 
tional throughout  the  life  of  the  female.  The  second  group 
includes  the  genus  Lecanium  and  others,  such  as  the  common 
black  scale  and  the  cottony  maple-scale.  The  young  insects  of 
this  group  wander  about  freely  for  a  while,  but  before  they  are 
half  grown  they  insert  their  long  projecting  mouth-parts  into 
the  tissues  of  the  plant  and  remain  stationary  for  the  rest 
of  their  life.  The  body-wall  becomes  dark  and  hard,  often 
very  convex  or  hemispherical,  and  usually  all  resemblance 
to  an  insect  is  lost.  The  third  group  includes  those  species 
that  have  the  body  concealed  by  a  scaly  covering  made  up  of 
a  waxy  secretion  in  which  is  imbedded  the  molted  skins  of 
the  insect  The  San  Jose  scale,  the  oyster-shell  scale,  the 
rose-scale,  and  others,  are  examples  of  this  group.  With 
the  second  molt  the  female  loses  her  eyes,  antennae  and  legs, 
and  becomes  a  sac-like  creature  covered  over  with  its  protect- 
ing scale  and  with  its  long  beak  thrust  into  the  plant  tissue. 

In  the  first,  or  mealy-bug,  group,  the  eggs  of  many  species 
issue  from  the  body  before  they  are  hatched,  the  female  often 


444    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

secreting  white  filamentous  or  flocculent  masses  of  wax  which 
protect  the  eggs.  In  the  other  groups  the  eggs  may  be  hatched 
within  the  body  of  the  mother  and  the  young  produced  alive,  or 
they  may  be  protected  underneath  her  body,  or  under  the  waxy 
scale,  until  they  hatch.  The  young,  or  larvae,  of  all  the 
species  are  very  similar,  being  minute,  mite-like,  little  creatures 
that  move  about  freely  for  a  while.  It  is  in  this  stage  that 
they  scatter  over  the  different  parts  of  the  tree  and  sometimes 
even  to  different  trees  or  orchards.  The  females  molt  twice 
during  their  development.  With  some  there  is  little  change 
in  the  appearance  of  the  insect  after  these  molts,  but  with 
others,  as  we  have  seen,  the  changes  may  be  very  remarkable. 
During  the  first  stage,  and  often  during  the  second  also,  the 
males  and  females  are  very  much  alike,  but  in  their  further 
development  the  male  makes  one  more  molt  than  the  female 
and  enters  a  pupal  stage  in  which  the  appendages  of  the  future 
adult  can  be  clearly  seen  folded  against  the  sides  of  the  body. 
The  adult  males  that  issue  from  these  pupae  are  remarkable 
in  several  respects.  Although  belonging  to  the  order  Hemip- 
tera,  the  adults  of  which  normally  have  two  pairs  of  wings, 
the  male  Coccids  have  only  one  pair,  the  second  pair  being 
represented  by  two  slender,  little,  hooked  organs  which  hook 
over  the  hind  margin  of  the  wings.  They  have  no  mouth-parts 
or  mouth-opening  for  taking  food.  In  the  place  where  the 
mouth-parts  are  usually  situated  there  is  an  extra  pair  of 
eyes.  In  many  species  the  end  of  the  abdomen  is  provided 
with  long,  pointed,  stylet-like  processes. 

As  the  females  never  acquire  wings,  and  as  the  larvae  are  so 
small  that  they  can  crawl  for  only  a  few  yards  at  the  most, 
it  is  evident  that  these  insects  must  depend  on  some  agencies 
besides  their  own  powers  of  locomotion  for  their  general  dispersal. 
The  active  young  larvae  may  crawl  on  the  feet  of  birds,  or  upon 
insects,  such  as  the  ladybird-beetles  or  the  ants  that  are  often 
found  on  trees  that  are  infested  with  the  scale-insects,  and  thus 
be  carried  for  considerable  distances  to  other  trees  or  to  near-by 
orchards.  Or  they  may  crawl  on  the  ladders  or  boxes  or  other 
articles  that  are  used  in  gathering  the  fruit.  It  is  evident,  how- 
ever, that  nursery  stock  or  budding  or  grafting  materials,  are  the 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   445 

chief  agencies  by  which  scale-insects  are  transferred  over  any 
great  distances.  The  fact  that  most  of  them  are  very  small 
and  inconspicuous  makes  it  an  easy  matter  for  them  to  es- 
cape detection,  and  thus  important  species  are  often  introduced 
into  new  regions  even  when  a  close  watch  is  being  kept  for 
them.  For  the  same  reason  nursery  stock  and  imported  plants 
of  various  kinds  are  the  principal  means  of  transferring  these 
pests  from  one  country  to  another. 

Besides  the  damage  that  the  scale-insects  do  by  sucking  the 
juices  from  the  plant,  and,  in  some  instances  at  least,  poisoning 
the  tissues  on  which  they  are  feeding,  they  may  secrete  a  con- 
siderable amount  of  honey-dew,  which  makes  the  leaves, 
branches  and  fruit  sticky  and  disagreeable  to  handle,  and  fur- 
nishes a  medium  in  which  a  black  sooty  fungus  grows.  Badly 
infested  trees  present  a  very  disgusting  appearance,  and  the 
fruit  is  often  unfit  for  use  until  it  is  washed  thoroughly  to 
remove  these  substances.  Many  insects,  particularly  the 
ants,  are  very  fond  of  this  honey-dew  and  feed  on  it  as  they  do 
on  the  honey-dew  secreted  by  the  aphids. 

The  list  of  scale-insects  known  to  attack  orchard  trees  is  a 
long  one,  but  we  shall  note  only  a  few  of  the  most  important. 

The  San  Jose  Scale  (Aspidiotus  perniciosus). — The  San 
Jose  scale  is  probably  the  most  important  of 'all  the  scale-in- 
sects, as  it  has  become  distributed  over  the  whole  United  States 
and  is  responsible  for  the  death  of  many  thousands  of  orchard 
trees  and  the  loss  of  much  fruit  in  orchards  in  which  the  trees 
are  not  killed  but  seriously  weakened.  This  insect  was  prob- 
ably introduced  into  America  from  China,  and  was  first  dis- 
covered on  some  trees  in  an  orchard  near  San  Jose,  California. 
Thus  it  came  to  be  popularly  known  as  the  San  Jose  scale. 

The  covering  wax  scale  of  this  insect  is  so  small  and  flat 
and  so  closely  resembles  the  color  of  the  bark,  that  it  makes 
the  insects  very  difficult  to  detect,  especially  when  there  are 
only  a  few  on  a  tree.  On  the  fruit  or  leaves  or  new  branches 
their  presence  is  more  easily  detected  on  account  of  the  con- 
spicuous red  spot  that  usually  surrounds  them.  When  the 
tree  is  badly  infested  the  scales  often  form  a  complete  crust 
over  the  bark  and  branches,  giving  them  a  characteristic 


446    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

grayish  appearance.  If  a  piece  of  the  outer  bark  of  the  in- 
fested tree  is  cut  away  the  cambium  will  be  seen  to  be  dis- 
colored by  numerous  red  spots,  which,  in  the  case  of  a  serious 
infestation,  may  coalesce,  staining  the  whole  outer  surface  of 
the  cambium.  The  scale  of  the  male  is  usually  darker  than 
that  of  the  female,  and  oblong-oval  instead  of  circular.  The 


FIG.  211. — San  Jose  scale,  Aspidiotus  perniciosus,  on  fruit,  leaves,  and 
stem  of  a  pear  tree.     (Reduced.) 

scales  of  the  young  of  the  male  and  female  are  alike,  both  being 
small  circular  and  black.  The  insect  passes  the  winter  in  the 
immature  condition  under  these  black  scales  on  the  trunk 
or  the  branches  of  the  tree.  In  the  early  spring  the  females 
become  mature  and  begin  to  produce  living  young.  The  young 
soon  make  their  way  from  underneath  the  scale  of  the  mother, 
and,  after  wandering  about  for  a  short  time,  settle  down  and 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   447 

begin  active  feeding.  Soon  after  this  they  begin  the  secre- 
tion of  the  waxy  substance  which  is  to  form  their  scaly 
covering.  Their  development  is  very  rapid  and  after  about 
thirty  days  they  themselves  begin  to  produce  living  young. 
Thus  there  may  occur  from  two  to  six  generations  during  the 
summer. 

There  are  several  kinds  of  parasites  that  are  of  more  or  less 
importance  in  controlling  the  San  Jose  scale,  but  none  of  these 
acts  quickly  enough  to  make  it  unnecessary  to  use  active  meas- 
ures in  fighting  the  pest.  Many  kinds  of  sprays  have  been 
tried,  but  the  sulphur-lime  spray  is  the  one  which  is  now  most 
generally  used.  The  directions  for  making  and  using  this  spray 
will  be  found  on  page  416.  Before  spraying,  the  trees  should 
be  pruned  back  as  much  as  is  practicable  so  that  all  of  the 
remaining  wood  may  be  thoroughly  covered.  In  some  re- 
gions miscible  oils  are  extensively  used. 

There  are  four  or  five  other  species  of  scale-insects  that  look 
very  much  like  the  San  Jose  scale,  and,  indeed,  can  only  be 
distinguished  from  it  by  the  use  of  the  lens,  but  as  their  habits  are 
much  the  same  and  as  the  same  remedies  are  to  be  used  for 
them  they  need  not  be  especially  discussed. 

Oyster-shell  Scale  (Lepidosaphes  ulmi). — As  the  name  in- 
dicates, the  scale  of  this  insect  is  shaped  somewhat  like  an  elon- 
gate oyster  shell.  It  is  long  and  narrow,  usually  somewhat 
curved  toward  the  posterior  end.  The  color  varies  from  light 
brown  to  dark  brown.  This  is  a  very  common  pest  on  almost 
all  kinds  of  fruit  trees,  occurring  also  on  many  other  trees  both 
cultivated  and  wild.  As  it  is  large  enough  to  be  easily  seen 
it  is  perhaps  better  known  than  almost  any  other  species.  It 
passes  the  winter  in  the  egg  stage,  the  eggs  being  well  protected 
by  the  firm  tough  scale  under  which  they  lie.  In  many  regions 
only  a  single  brood  occurs  each  year,  but  in  the  South  there  may 
be  two  broods.  This  insect  is  subject  to  the  attack  of  several 
natural  enemies,  among  the  most  important  of  which  are  the 
chalcid-flies,  which  sometimes  control  the  pest  fairly  well.  It 
is  very  difficult  to  kill  the  eggs  by  spraying  in  the  winter,  but 
if  the  trees  are  thoroughly  sprayed  with  the  sulphur-lime  wash 
just  before  the  buds  open  most  of  the  young  will  be  killed  soon 


448    ECONOMIC  ZOOLOGY   AND  ENTOMOLOGY 


after  hatching.  Kerosene  emulsion  or  whale-oil  soap  or  other 
sprays  may  be  used  just  after  the  young  hatch  as  they  are 
very  easily  killed  before  they  are  protected  by  the  scale. 

The  Scurfy-scale  (Chionaspis  furfur  a). — This  scale  is  very 
common  on  apple  and  pear  trees,  but  may  also  attack  cherry, 
peach,  plum  and  many  other  trees.  The  scale  of  the  adult  fe- 
male is  whitish  or  dirty  gray,  flat,  and  irregu- 
larly ovate.  The  yellow  exuvium  is  at  the 
narrowed  anterior  end.  The  scale  of  the 
male  is  snow  white,  and  elongate  with  the 
sides  nearly  parallel.  The  males  and  the 
females  usually  occur  on  different  branches. 
They  pass  the  winter  in  the  egg  stage  and  so 
are  controlled  by  the  same  methods  as  are 
recommended  for  the  oyster-shell  scale. 

The  European  Fruit  Lecanium  (Lecanium 
corni). — There  are  several  species  of  scale- 
insects  that  belong  to  the  group  commonly 
known  as  Lecaniums,  but  as  they  are  similar 
in  appearance  and  habits  only  one  species 
will  be  described.  L.  corni  was  formerly 
known  under  many  different  names  as  it 
varies  somewhat  in  appearance  under  dif- 
ferent conditions  and  on  different  host  plants. 
In  many  regions  it  is  usually  known  as  the 
plum-scale.  In  the  west  it  is  commonly 
known  as  the  brown  apricot-scale.  It  is 
usually  quite  convex,  sometimes  almost  hemi- 
spherical, but  often  oval  or  even  pointed  at 
one  or  both  ends.  The  color  varies  from  light 
brown  to  dark  brown,  a  medium  reddish- 
brown  being  perhaps  the  prevailing  color. 
The  surface  is  usually  shiny  and  often  marked  by  fuscous 
transverse  or  longitudinal  markings  and  irregular  pits.  The 
young  insects  may  be  found  on  the  twigs  and  branches  of  the 
tree  during  the  winter  time,  as  it  passes  the  winter  in  the  im- 
mature stage.  Any  large  apparently  full-grown  scales  which 
may  be  found  during  the  winter  are  the  remains  of  the  dead 


FIG.  212.— The 
European  fruit 
Lecanium,  L. 
corni,  on  twig  of 
apricot  tree. 
(Natural  size) 


INSECTS  INJURIOUS  TO  ORCHARD  TREES   449 

bodies  of  mothers  that  have  laid  their  eggs  early  in  the 
summer.  A  small  chalcid-fly  is  a  very  common  parasite  of 
this  scale  and  often  controls  it  effectively  when  it  once  becomes 
well  established  in  an  orchard.  The  parasites  cannot  be 
depended  on  for  absolute  control,  however,  and  spraying  is 
usually  necessary.  The  sulphur-lime  spray  gives  very  good 
results,  but  some  prefer  a  kerosene  emulsion,  one  part  to  four 
parts  of  water,  or  a  5  per  cent,  or  6  per  cent,  distillate  oil 
emulsion.  The  spraying  should  be  done  in  the  winter  in  order 
that  the  over-wintering  young  may  be  killed. 


29 


CHAPTER  XXXIII 
INSECTS  AFFECTING  CITRUS  FRUITS 

Insect  pests  are  among  the  most  serious  obstacles  to  the 
successful  growing  of  citrus  fruits.  In  spite  of  the  fact  that 
California  growers  spend  more  than  half  a  million  dollars 
annually  in  fighting  the  scale-insects  (Coccidce)  in  their  orange 
and  lemon  groves,  the  losses  caused  by  these  pests  are  still 
enormous.  It  is  estimated  that  the  Florida  orange  growers 
would  receive  annually  at  least  one-half  million  dollars  more  for 
their  crop  if  the  white-fly,  Aleyrodes  citri,  could  be  exterminated 
in  their  groves. 

As  the  attack  on  citrus  trees  is  made  chiefly  by  a  few  insects 
that  are  closely  related  to  each  other,  and  hence  are  much  alike 
in  the  nature  of  their  injurious  feeding,  and  in  their  structure, 
life-history  and  general  habits,  the  remedies  for  the  citrus 
pests  are  less  various  than  those  used  in  the  warfare  against  the 
insect  enemies  of  the  deciduous  orchards.  Hence  certain 
generalizations  can  be  made  concerning  insect  attacks  on  citrus 
fruits  and  concerning  the  remedies  for  them. 

The  injuries  are  chiefly  caused  by  sap-sucking  insects  of  the 
order  Hemiptera.  These  insects,  though  small,  are  prolific 
breeders,  and  when  once  allowed  a  foothold  in  a  grove  increase 
rapidly  to  enormous  numbers.  They  suck  the  juices  from 
leaves  and  fruits,  causing  the  former  to  wilt  and  the  latter  to  be 
rendered  unmarketable.  As  most  of  the  citrus  insects  secrete 
honey-dew,  the  sooty  fungus,  Capnodium,  whose  spores  ger- 
minate freely  in  this  substance,  frequently  grows  in  a  close 
felted  mass  over  the  attacked  leaves  and  fruits,  not  only 
rendering  them  unsightly  and  disagreeably  dirty,  but  actually 
seriously  hurting  the  tree  by  interfering  with  the  functions  of 
the  leaves.  The  fungus  closes  the  stomata,  or  breathing  pores, 
in  the  leaves,  and  prevents  the  proper  exchange  of  gases  neces- 
sary to  the  tree's  health. 

450 


INSECTS  AFFECTING  CITRUS  FRUITS        45 1 

The  remedies  for  the  insect  pests  must  be  such  as  will  kill 
them  by  external  contact,  or  by  suffocating  them.  The  spray- 
ing of  arsenical  poisons  on  the  trees  would  have  no  effect,  for 
the  food  is  drawn  by  the  insects  from  below  the  surface. 
Fumigation  by  hydrocyanic  gas,  the  application  of  kerosene 
emulsions  or  similar  contact  poisons,  and  recourse  to  dis- 
tributing and  encouraging  the  natural  insect  enemies  of  the 
pests,  are  the  remedies  chiefly  used. 

The  following  paragraphs  give  brief  accounts  of  the  character 
and  life  of  a  number  of  the  more  important  of  the  pests. 
They  should  enable  those  students  who  have  opportunities  to 
visit  orange  and  lemon  groves  to  become  acquainted  with  the 
insects,  and  to  understand  the  means  of  controlling  them. 
Most  of  the  citrus  fruit  pests,  it  will  be  noted,  are  scale-insects 
and,  therefore,  the  general  account  of  these  insects  given  in 
Chapter  XXXII  should  be  referred  to  in  connection  with 
the  accounts  in  this  chapter  of  various  species  of  the  group. 

The  White-fly  (Aleyrodes  «><).— This  is  by  far  the  most 
important  pest  of  the  citrus  trees  in  the  Gulf  states.  The 
adults  are  small  white  insects  with  two  pairs  of  wings  covered 
with  a  white  waxy  powder,  which  has  suggested  the  popular 
names  of  "white-fly"  or  "mealy-wings."  These  insects  prefer 
to  rest  in  quiet  shady  places,  hence  they  are  less  common  in  dry 
open  groves  than  they  are  in  groves  where  the  foliage  is  dense 
and  there  is  considerable  moisture.  The  eggs  are  laid  on  the 
underside  of  the  leaves,  preferably  on  new  leaves.  The  young 
larvae  are  similar  in  appearance  to  young  scale-insects,  and 
move  about  freely  for  a  short  time  before  they  settle  on  the 
underside  of  the  leaves  and  begin  feeding.  As  they  are 
whitish-green  in  color  and  translucent  they  are  hard  to  see. 
The  pupal  stage,  which  is  entered  a  few  weeks  later,  is  similar 
in  appearance  to  the  later  larval  stages.  There  are  usually 
three  broods  during  the  year.  As  the  undersides  of  the  leaves 
are  often  almost  completely  covered  with  these  pests  the 
injury  that  they  may  do  by  sucking  the  juices  from  the  leaf 
tissues  is  often  very  great.  Perhaps  the  greatest  injury,  how- 
ever, is  caused  by  the  sooty  mould  that  grows  in  the  honey-dew 
that  is  secreted  by  these  insects.  This  honey-dew  drops  on  the 


452    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

leaves  and  fruit,  and  the  fungus  growing  in  it  forms  a  thin 
covering  that  seriously  interferes  with  the  function  of  the  leaf 
and  very  materially  damages  the  fruit. 

Certain  fungus  diseases  that  attack  the  white-flies  often 
control  them  quite  effectually  but  it  is  sometimes  necessary  to 
resort  to  spraying.  The  resin  wash  has  been  much  used.  A 
spray  made  by  thoroughly  emulsifying  two  gallons  of  paraffine 
oil  with  one  gallon  of  whale-oil  soap  and  one  gallon  of  water  is 
strongly  recommended.  One  gallon  of  the  stock  emulsion 
should  be  used  in  fifty  gallons  of  water.  December,  January, 
and  February  are  the  best  months  to  spray  for  these  insects,  as 
practically  all  of  them  are  then  in  the  larval  stage.  As  it  is 
very  difficult  to  reach  thoroughly  all  of  the  foliage  on  an  orange 
or  lemon  tree  with  any  spray  mixture,  it  is  much  more  satis- 
factory, where  possible,  to  fumigate  with  hydrocyanic  acid  gas. 
If  properly  done  at  the  season  suggested  for  spraying,  it  will 
effectively  control  the  white-fly. 

There  are  two  other  species  of  white-fly,  A.  nubifera,  and  A. 
howardi,  affecting  citrus  trees,  but  they  are  similar  in  appear- 
ance and  habits  to  A .  citri. 

Black  Scale  (Saissetia  olea). — This  is  perhaps  the  most 
important  scale-insect  on  the  orange  trees  of  the  Pacific 
Coast,  not  so  much  on  account  of  the  direct  injury  caused  by 
the  loss  of  sap,  which  the  myriads  of  insects  are  con- 
stantly drawing  from  the  leaves  and  branches,  but  because, 
like  the  white-fly,  it  secretes  a  great  deal  of  honey-dew  in  which 
a  sooty  mould  grows.  This  is  an  insect  widely  spread  over  the 
world  and  long  known  as  a  pest  of  olives  and  oleanders.  The 
adult  female  is  almost  hemispherical  in  shape,  a  little  longer 
than  broad,  hard  or  leathery  in  texture  and  dark  brown  or 
black  in  color.  The  younger  stages  are  flatter  and  on  the 
dorsal  side  are  marked  by  one  longitudinal  and  two  transverse 
ridges,  forming  the  letter  "H."  The  adult  also  shows  this  H, 
but  less  plainly.  The  black  scale  is  not  nearly  as  serious  a  pest 
in  the  Gulf  region  as  it  is  on  the  Pacific  Coast. 

In  1900  there  was  introduced  into  California  a  small  Hymen- 
opterous  parasite,  Scutellista  cyanea,  of  the  black  scale  that 
has  proved  to  be,  in  some  localities  at  least,  an  important  factor 


INSECTS  AFFECTING  CITRUS  FRUITS        453 


in  its  control.  Sometimes  as  high  as  80  per  cent,  of  the  scales 
will  show  the  small  hole  whence  the  adult  parasite  has  escaped 
from  its  host.  Yet  the  numbers  of  living  scales  that  are  left  are 
great  enough  often  to  make  it  necessary  to  use  some  artificial 
methods  of  control.  Most  growers  rely  on  fumigation  to  con- 
trol this  pest,  but  in  some  cases,  especially  in  the  case  of  young 
trees,  it  is  practical  to  spray.  The  kerosene  sprays  discussed 
on  page  416,  have  been  found  most  satisfactory. 


FIG.  213. — Black  scale, 
Saissetia  olea,  on  orange 
twig.  (Slightly  en- 
larged.) 


FIG.  214. — Young  of  black  scale, 
Saissetia  olece.  (About  seventy  times 
natural  size;  after  Quayle,  photo  by 
Doane.) 


The  hemispherical  scale,  S.  hemispharica,  looks  very  much 
like  the  black  scale,  but  the  dorsal  surface  is  smooth  and  shining 
and  does  not  have  the  ridges  that  form  the  letter  H.  It  is 
often  found  on  citrus  trees  out  of  doors,  but  is  a  more  common 
pest  in  greenhouses,  where  it  attacks  many  kinds  of  plants. 
The  soft  brown  scale,  Coccus  hesperidum,  is  also  sometimes 


454    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

associated  with  the  black  scale,  but  is  easily  distinguished  be- 
cause of  its  reddish-brown  or  yellowish  color  and  by  minute 
darker  spots  or  bars  on  its  dorsal  surface  which  may  form  more 
or  less  distinct  radiating  lines.  It  is  elongate  oval  in  shape. 
It  is  often  very  abundant  on  the  trees,  where  it  does  con- 
siderable damage  by  taking  sap  from  the  plant.  This  species 
is  attacked  by  three  or  four  kinds  of  internal  parasites  that 
usually  keep  it  well  in  control,  so  that  the  grower  does  not  often 
have  to  resort  to  sprays  or  fumigation. 

The  Red  Scale  of  California   (Chrysomphalus  auranti.}— 
This  is  one  of  the  most  destructive  scale  insects  in  California. 


FIG.  215. — Red  scale,  Chrysomphalus  duranti,  on  lemon  leaf.      (Enlarged; 
after  Quayle,  photo  by  Doane.) 


Unlike  the  black  scale  it  does  not  secrete  the  honey-dew  in 
which  the  sooty  mold  grows,  but  the  direct  effect  of  the  attack 
on  the  tree  is  much  more  serious.  It  attacks  all  parts  of  the 
tree,  trunk,  branches,  twigs,  leaves  and  fruit.  The  trees  are 
often  killed  within  two  or  three  years  after  the  first  infestation 
if  they  are  not  properly  cared  for.  Even  when  the  insects 


INSECTS  AFFECTING  CITRUS  FRUITS        455 

are  not  abundant  enough  to  injure  the  tree  seriously  they  may 
cause  considerable  loss  by  their  presence  on  the  fruit.  Atten- 
tion is  usually  called  to  the  pest  by  the  presence  of  small  light 
yellowish  spots  on  the  leaves.  The  scale  of  the  female  is 
almost  circular  in  outline,  very  flat,  and  about  one-thirty-sec- 
ond to  one-sixteenth  of  an  inch  in  diameter.  The  scale  of  the 
male  is  more  elongate.  This  insect  increases  in  numbers  so 
rapidly  that  although  it  is  attacked  by  several  natural  enemies 
it  is  necessary  to  take  active  measures  early  to  control  it  when 
it  gains  a  foothold  in  the  orchard.  Fumigation  is  the  most 
practical  remedy. 

The  yellow  scale,  a  variety  of  the  red  scale,  is  very  similar  in 
appearance  and  habits  to  the  red  scale,  and  is  only  distin- 
guished from  it  by  its  lighter  color.  It  confines  its  attacks  to 
the  leaves  and  fruit,  seldom  attacking  the  twigs  or  branches. 

The  red  scale  of  Florida,  C.  aonidum,  is  similar  in  appearance 
to  the  red  scale  of  California,  but  the  waxen  cover  is  heavier 
and  darker,  usually  reddish-brown  or  almost  black  with  a 
whitish  spot  in  the  center.  It  is  of  little  importance  as  an 
enemy  of  citrus  trees,  but  is  often  a  serious  pest  in  greenhouses. 

The  Purple  Scale  (Lepidosaphes  becki). — In  general  ap- 
pearance this  scale  is  very  much  like  the  oyster-shell  scale  that 
occurs  on  the  apple  trees.  It  attacks  all  parts  of  the  trees, 
the  leaves,  branches,  trunk  and  fruit  frequently  becoming 
entirely  covered  by  the  pest.  It  may  cause  the  leaves  or  fruit 
to  drop,  or  may  even  kill  part  of  the  tree,  but  it.  seldom  kills 
the  entire  tree  and  so  is  not  as  serious  a  pest  as  the  red  scale. 
It  occurs  in  destructive  numbers  throughout  the  citrus  regions 
of  Florida  and  the  Gulf  states  and  in  certain  sections  of  Califor- 
nia. The  female  insect  occupies  only  the  anterior  portion  of  the 
scale,  the  posterior  portion  being  full  of  eggs  and  growing  to 
meet  the  requirements  as  more  eggs  are  produced.  The  young, 
soon  after  hatching,  make  their  way  from  beneath  the  pro- 
tecting scale,  settle  on  the  plant,  and  begin  secreting  the  waxy 
substance  that  is  to  form  their  scale-like  covering.  It  is 
toward  the  destruction  of  these  younger  scales  that  the 
orchardist  must  direct  his  attention,  for  the  old  insects  are  so 
well  protected  that  it  is  difficult  to  kill  them  with  any  ordinary 


456    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

spray  or  even  by  fumigation,  nor  will  the  fumigation  affect 
the  eggs.  On  badly  infested  trees  it  is  usually  necessary  to 
give  two  treatments,  the  second  about  six  weeks  or  two 
months  later  than  the  first,  in  order  that  the  young  which 
hatch  after  the  first  treatment  may  be  killed.  The  dosage 
used  in  fumigating  for  the  purple  scale  is  one-fourth  to  one- 
third  stronger  than  that  used  for  the  red  scale. 


FIG.  216. — Purple   scale,    Lepidosaphes    becki.      (Much    enlarged;    after 
Quayle,  photo  by  Doane.) 

Glover's  Scale  (Lepidosaphes  gloveri). — The  waxen  scale  of 
this  insect  resembles  that  of  the  purple  scale,  but  is  longer  and 
narrower  and  less  curved,  hence  it  is  often  known  as  the  long 
scale.  It  is  a  serious  pest  in  Florida  and  the  Gulf  region,  but  has 
never  become  a  pest  in  California.  The  life  history  and  habits 
are  much  the  same  as  those  of  the  purple  scale,  and  the  remedies 
to  be  used  are  the  same. 

The  Chaff  Scale  (Parlatoria  pergandi) . — The  scales  covering 
the  females  of  this  species  are  whitish,  rounded  or  oval,  with 
the  molted  skin  close  to  one  margin.  The  scale  of  the  male 
is  similar,  but  more  elongate.  They  are  usually  found  on  the 
trunk  and  branches  of  the  tree,  but  may  also  occur  on  the 


INSECTS  AFFECTING  CITRUS  FRUITS        457 

fruit.  The  insect  is  destructive  to  citrus  trees  in  Florida  and 
the  other  Gulf  states,  but  does  not  occur  in  California.  It  is 
very  often  found  as  a  pest  in  greenhouses  in  many  sections  of 
the  United  States.  When  the  scales  occur  on  parts  of  the 
tree  that  can  readily  be  reached  with  sprays  they  may  be  com- 
paratively easily  controlled  by  spraying  with  kerosene  emul- 
sion; otherwise,  fumigation  should  be  resorted  to. 

The  Mealy-bug  (Pseudococcus  citri}. — This  insect  is  one  of 
those  kinds  of  Coccidce  that  are  unprotected  by  any  scaly 
covering.  The  body  is  covered  with 
a  mealy  or  flocculent  waxy  secretion 
which,  on  the  sides,  takes  the  form 
of  short  waxy  filaments.  The  two 
posterior  filaments  are  two  or  three 
times  as  long  as  those  on  the  sides. 
The  insects  are  active  during  all  the 
stages  of  their  development  until  the 
female  begins  to  secrete  the  loose, 
fluffy,  cottony  mass  that  serves  to 
protect  the  eggs.  The  females  may 
begin  laying  eggs  when  they  are  only 
five  or  six  weeks  old,  and  as  each  fe- 
male will  lay  from  three  to  four  hun- 
dred eggs  the  number  of  individuals 

in  a  colony  increases  very  rapidly.    fseMococctacunf    ^reauy 
They  may  attack  any  part  ol  the    enlarged;   after  Quayle, 
tree,  but  are  usualy  found  in  pro-    photo  by  Doane.) 
tected  places,  such   as  the  base  of 

the  leaves,  in  the  navel  of  the  orange,  or  in  places  where  the 
leaves  or  the  fruit  touch  each  other  or  some  other  object.  These 
insects  secrete  considerable  honey-dew,  which  is  so  very  sticky 
that  it  takes  much  washing  and  brushing  to  remove  it  and  the 
smutty  fungus  that  grows  on  it  from  the  fruit.  Aside  from 
the  cost  of  the  labor  required  to  clean  the  fruit,  this  washing 
is  undesirable  because  it  affects  the  keeping  qualities  of  the 
oranges  and  lemons. 

On  account  of  their  habit  of  hiding  away  in  protected  places, 
and  because  the  cottony  secretion  that  covers  them  is  so  hard 


458    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

to  penetrate,  mealy-bugs  are  among  the  most  dreaded  pests  in 
the  orange  and  lemon  orchards.  Any  of  the  sprays  used  at 
ordinary  strength  will  leave  many  of  them  unharmed.  A  strong 
carbolic  acid  spray,  made  as  suggested  on  page  417  and  applied 
under  a  very  high  pressure,  is  the  most  efficient  remedy  yet 
found.  Two  or  three  or  even  more  applications  are  often 
necessary  before  the  insects  can  all  be  destroyed.  Fumiga- 


FIG.  218. — Mealy-bugs,  Pseudococcus  citri,  on  lemons.     (Reduced,-  after 
Quayle,  photo  by  Doane.) 

tion  as  ordinarily  used  on  citrus  trees  does  not  kill  nearly  all 
of  the  mealy-bugs,  and  for  this  reason  has  not  proved  as  satis- 
factory as  some  of  the  sprays. 

The  mealy-bugs  are  attacked  by  several  parasites  and  pre- 
daceous  insects.  The  ladybird-beetles  are  particularly  im- 
portant in  the  control  of  this  pest.  The  larvae  of  one  of  these 
little  beetles,  Cryptolcemus  montrouzieri,  is  covered  with 
cottony  tufts  making  it  look  very  much  like  the  mealy-bug 


INSECTS  AFFECTING  CITRUS  FRUITS 


459 


as  it  feeds  among  them.     The  larvae  of  lace-wing  flies  and 
syrphus-flies  also  destroy  many  mealy-bugs. 

The  Cottony-cushion  Scale  (I  eery  a  purchast).—This  insect 
was  at  one  time  the  most  serious  pest  of  the  citrus  fruits  in 
California  where  it  destroyed  many  groves  of  citrus  trees  and 


FIG.  219. — Cottony-cushion  scale,  Icerya  purchasi,  on  orange  tree.  A 
few  young  are  seen  on  the  white  egg  sacs.  (About  natural  size;  after 
Quayle,  photo  by  Doane.) 

many  ornamental  plants.  It  has  not  appeared  in  destructive 
numbers  in  other  parts  of  the  United  States.  It  was  intro- 
duced into  California  from  Australia  about  1868,  and  within 
ten  years  had  become  very  abundant  and  destructive,  particu- 
larly in  the  southern  part  of  the  state.  For  some  years  the 
orange  and  lemon  growers  fought  against  it  unsuccessfully. 


460    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Finally  an  entomologist  was  sent  to  Australia  to  study  the  pest 
in  its  native  home  and  see  if  some  natural  enemy  could  not 
be  found  that  would  help  to  control  it.  Among  other  things 
that  he  sent  back  were  colonies  of  the  small  ladybird-beetle 
now  commonly  known  as  the  Australian  ladybird,  Novius 
( Vedalia)  cardinalis,  and  within  a  remarkably  short  time  this 
little  beetle,  both  the  larvae  and  adults  of  which  feed  exclu- 
sively upon  this  scale,  had  so  reduced  the  numbers  of  the  pest 
that  it  was  practically  under  control,  and  since  that  time  the 
cottony-cushion  scale  has  not  been  regarded  as  a  serious  pest. 
As  soon  as  it  appears  in  considerable  numbers  on  any  trees 
or  plants  some  of  the  twigs  or  branches  are  cut  off  and  sent 
to  the  State  Horticultural  Commissioner  who  in  return  sends 
out  a  small  colony  of  the  ladybird-beetles,  if  he  finds  that  they 
are  not  already  present  among  the  specimens  that  are  sent  in. 
The  large  cottony  egg  sac  of  the  female  scale  is  longitudinally 
ribbed  or  fluted,  and  is  a  conspicuous  object  that  is  not  likely 
to  be  mistaken  for  any  other  insect.  The  young  are  some- 
times found  on  the  leaves  where  they  are  easily  recognized  by 
the  light  cottony  secretion  and  the  large  glass-like  filaments 
that  project  from  parts  of  the  body.  As  the  ladybird-beetles 
keep  it  so  well  in  control  it  is  rarely  necessary  to  take  any  other 
measures  to  combat  it. 

Florida  Wax -scale  (Ceroplastes  floridensis] . — Although  this 
insect  seldom  appears  in  great  numbers  on  the  orange  or  lemon 
trees,  its  striking  appearance,  when  it  is  present  at  all,  at 
once  attracts  attention  to  it  and  sometimes  occasions  consider- 
able needless  alarm.  The  young,  which  are  seen  on  citrus  trees 
more  commonly  than  the  adults,  are  covered  with  a  white  waxy 
secretion  that  radiates  from  the  center  so  that  the  very  young 
insect  looks  like  a  small  oval  white  star.  As  the  insect  grows 
older  the  waxy  covering  becomes  more  or  less  distinctly 
separated  into  six  or  eight  plates.  The  color  is  white  with  a 
pinkish  tinge. 

The  Barnacle -scale  (C.  cirripedijormis),  looks  somewhat 
like  the  preceding  but  is  much  larger  and  the  waxy  plates 
are  more  distinctly  marked,  each  plate  being  mottled  with 
grayish  or  light  brown.  As  these  insects  rarely  become  at 


INSECTS  AFFECTING  CITRUS  FRUITS        461 

all  abundant  it  is  seldom  necessary  to  use  any  methods  of 
control. 

The  Orange  Thrips  (Euthrlps  citri}.— Within  the  last  few 
years  certain  thrips  have  been  doing  considerable  damage  to 

(the  oranges  in  some  parts  of  California.  They  usually 
work  around  the  stem  or  depressions  in  the  skin,  making  dis- 
tinct whitish  marks  which,  while  not  affecting  the  edible 
qualities  of  the  fruit,  seriously  affect  its  market  value,  as  such 
fruit  cannot  be  graded  as  first  class.  The  insects  themselves 
are  very  minute,  and  are  seldom  noticed  unless  looked  for  very 
carefully.  Spraying  is  the  most  satisfactory  means  of  con- 
trol. The  sulphur-lime  spray  (see  page  415)  is  the  one  most 
commonly  used.  It  is  necessary  to  use  great  care  to  reach 
all  parts  of  the  tree,  and  a  high  pressure  is  essential.  There 
are  other  species  of  thrips  that  attack  the  orange,  but  their 
habits  are  the  same  and  they  yield  to  the  same  methods  of 
control. 

There  are  several  other  orange  pests,  such  as  Fuller's  rose 
beetle,  Aramigus  fullerl,  and  the  diabrotica  beetle,  Diabrotica 
soror,  which  feed  on  the  leaves,  doing  particular  damage  to 
young  shoots  or  to  new  grafts.  The  red  and  silver  mites  are 
referred  to  on  page  213.  The  larvae  of  certain  moths  attack 
the  fruit  and  sometimes  the  leaves  also,  but  these  are  usually 
of  little  importance. 

The  Mexican  Orange  Maggot  (Trypeta  ludens). — This  insect 
has  not  yet  established  itself  in  the  United  States.  It  is,  how- 
ever, a  serious  pest  of  oranges  in  Mexico,  and  there  is  always  a 
possibility  of  its  gaining  an  entrance  into  this  country  in  spite 
of  the  strict  quarantine  which  is  established  against  it.  The 
larvae,  or  maggots,  feed  in  the  pulp  of  the  orange.  When 
fully  developed  the  larvae  enter  the  ground  and  pupate.  The 
adult  fly  is  yellowish  in  color,  and  has  transparent  wings 
marked  with  brownish  bands. 


CHAPTER  XXXIV 
INSECTS  INJURIOUS  TO  VINEYARDS  AND  BERRIES 

The  small  fruits  have  their  insect  enemies  no  less  than  the  or- 
chard fruits.  Grapes,  currants,  berries,  all  have  a  constant 
struggle  against  insect  pests,  and  call  for  our  help  in  no  uncer- 
tain tones.  A  quarter  of  a  century  ago  the  enormously  valu- 
able vineyards  of  France  seemed  to  be  on  the  point  of  total 
destruction  from  the  insidious  attacks  of  a  minute  soft-bodied 
delicate-winged  aphid,  the  grape  phylloxera,  that  carried  on 
most  of  its  deadly  work  underground  and  hence  was  hardly 
visible  to  the  appalled  vineyardists.  And  later,  in  the  exten- 
sive vineyards  of  California  a  similar  tale  of  destruction  began 
to  be  told.  The  French  government  offered  a  great  reward  to 
any  one  who  should  devise  an  effective  remedy  for  the  pest,  and 
scores  of  entomologists  gave  their  whole  time  to  the  study  of  the 
life  of  the  insect.  Finally  it  was  found  that  certain  American 
wild  grapes  had  developed  a  natural  resistance  or  immunity  to 
the  attacks  of  the  pest,  and  grape-growing  was  revolutionized 
by  the  adoption  of  the  practice  of  grafting  the  valuable  but  deli- 
cate wine  grape  kinds  on  to  the  strong  resistant  wild  roots.  As 
the  kind  of  fruit  is  determined  by  the  graft  and  not  by  the  stock 
this  combination  has  proved  the  saving  of  the  great  vine  indus- 
try of  Europe  and  California. 

Among  the  other  grape  pests  are  several  kinds  of  beetles,  the 
adults  of  which  eat  the  leaves  while  their  larvae  attack  the  roots, 
leaf-hoppers  which  take  sap  from  the  leaves  and  tendrils  by 
means  of  their  sharp  little  piercing  and  sucking  beak,  and  the 
larvae  of  certain  small  moths  which  eat  both  leaves  and  the 
grapes  themselves. 

Among  the  more  important  enemies  of  raspberries  and  black- 
berries are  the  active,  strong-jawed  larvae  of  certain  clear- 
winged  moths  (Sesiidte)  and  certain  beetles.  These  are  vari- 
ously called  cane-borers,  crown-borers  and  root-borers  because 

462 


INSECTS  INJURIOUS  TO  BERRIES  463 

they  mine  the  plants  in  these  various  parts  of  it.  Scale-insects 
and  slugs  (larvae  of  saw-flies)  also  do  much  damage. 

Currants  and  gooseberries  suffer  from  cane-borers,  slugs, 
aphids  and  scale-insects,  and  from  the  effective  girdling  opera- 
tions of  a  saw-fly  that  attacks  the  stems.  Certain  flies  lay 
their  eggs  in  the  berries,  and  the  hatching  larvae  burrow  in  and 
feed  on  the  pulp  and  seeds 

Strawberries  have  an  unusual  number  of  insect  enemies, 
including  weevils,  aphids  and  the  boring  larvae  of  various  moths 
and  beetles. 

For  all  these  various  pests  remedies  have  to  be  devised  with 
special  care  and  ingenuity  because  of  the  tenderness  of  the 
plants  and  the  fact  that  it  is  the  berries  themselves  which  are 
so  often  attacked  and  which,  of  course,  cannot  be  poisoned. 
Careful  pruning  of  partly  infested  plants  and  the  complete 
cutting  out  and  burning  of  more  seriously  attacked  plants  are 
largely  resorted  to  by  berry  growers.  However,  arsenical 
sprays  and  emulsions  of  whale-oil  soap  and  kerosene  have  their 
place  in  the  fighting,  as  well  as  a  number  of  special  remedies 
applicable  to  the  particular  conditions  under  which  berries  are 
grown. 

Students  in  any  locality  will  have  no  difficulty  in  getting  per- 
sonally acquainted  with  some,  at  least,  of  the  most  important  of 
the  grape  and  berry  pests  described  in  the  following  paragraphs. 
For  accounts  of  others,  government  and  state  bulletins,  horti- 
cultural books  and  manuals  of  injurious  insects  may  be  re- 
ferred to. 

GRAPES 

The  Grape-vine  Phylloxera  (Phylloxera  vastatrix) . — The  in- 
sect referred  to  in  the  first  paragraph  of  this  chapter  is  a  small 
brownish  plant-louse  or  aphid,  which  is  commonly  called  by  its 
generic  name,  phylloxera.  It  may  occur  in  four  different 
forms.  During  the  fall  there  appears  a  sexual  generation 
which  lays  the  winter  eggs  under  the  rough  bark  of  the  vine. 
These  hatch  early  in  the  spring,  and  some  of  the  young  aphids 
crawl  out  to  the  leaves  where  they  produce  small  but  conspicu- 
ous reddish  galls.  This  leaf  feeding  form  rarely  occurs  on  the 


464    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

European  varieties  of  grapes,  and  probably  does  not  occur  at 
all  in  California.  Most  of  the  young  which  hatch  from  the 
winter  eggs  crawl  down  to  the  roots,  where  their  feeding  causes 
small  cancerous  swellings  or  galls.  Generation  after  genera- 
tion of  wingless  individuals  may  be  produced  on  the  roots  with- 
out any  winged  or  sexual  forms  appearing,  so  that  the  whole 
root  system  may  soon  become  badly  infested.  As  the  at- 


FIG.  2 20. — The  grape  phylloxera,  Phylloxera  vastatrix.  In  the  upper 
left-hand  corner  an  egg  from  which  a  male  has  issued,  next  an  egg  from 
which  a  female  has  issued;  in  upper  right-hand  corner,  winter  egg;  at  left- 
hand  of  middle  row,  a  just-hatched  young,  next  a  male  (note  absence  of 
mouth-parts);  at  right  end  of  middle  row,  female;  lower  figure,  winged 
form.  (Much  enlarged;  after  Ritter  and  Riibsaamen.) 


tacked  roots  soon  decay,  the  vitality  of  the  vine  is  seriously 
affected  and  it  usually  dies  within  a  short  time.  Sometimes, 
during  the  summer,  a  winged  generation  of  females  may  appear. 
These  make  their  way  to  the  surface,  fly  to  other  plants  and  lay 
eggs  there  of  two  sizes.  The  smaller  of  these  eggs  produce  the 
males  and  the  larger  the  females  of  the  sexual  generation  that 
lays  the  winter  eggs. 


INSECTS  INJURIOUS  TO  BERRIES  465 

No  satisfactory  remedies  for  controlling  the  pest  in  badly  at- 
tacked vineyards  have  yet  been  found.  Carbon  bisulphide  is 
sometimes  introduced  into  the  ground  around  the  vines  and 
many  of  the  root-inhabiting  aphids  thus  destroyed.  Flooding 
has  been  resorted  to  in  some  regions,  but  such  methods  are  either 
too  expensive  or  are  possible  only  in  certain  localities.  When 
any  of  the  vines  are  found  to  be  unthrifty  or  dying,  the  roots 
should  be  examined  carefully  and,  if  the  insect  is  found,  all  of 
the  vines  in  the  affected  portion  of  the  vineyard  should  be  dug 
out  and  burned. 

But  the  principal  remedy  for  the  phylloxera  is  the  replanting 
of  the  vineyard  on  "resistant"  roots.  The  pest  is  a  native 
of  America,  and  the  wild  grapes  of  this  country  have  come  to  be 
naturally  immune,  or  resistant,  to  the  attacks  of  the  insect. 
Grafting  the  European  cultivated  varieties  on  to  the  wild  or 
only  slightly  modified  American  varieties  is  therefore  an  effect- 
ive means  of  escaping  the  ravages  of  the  pest. 

Phylloxera  was  first  made  known  in  New  York  in  1853,  and 
was  soon  discovered  to  be  well  scattered  over  the  wild  vines  in  the 
eastern  United  States.  It  was  introduced  into  France  about 
1863,  and  increased  with  such  rapidity  that  in  twenty  years  it 
had  destroyed  more  than  one-third  of  all  the  vineyards  of  that 
country  and  had  affected  most  of  the  others.  It  was  intro- 
duced into  California,  where  French  varieties  of  grapes  are 
largely  grown,  about  1874,  and  by  1900  many  thousands  of 
acres  of  vineyards  had  been  destroyed.  The  vineyards  of  both 
Europe  and  California  are  now  chiefly  planted  on  resistant 
roots. 

The  Grape-root  Worm  (Fidia  viticida). — The  adult  of  this 
insect  is  a  chestnut-brown  beetle  that  appears  on  the  vines 
about  the  close  of  the  blooming  season  and  begins  feeding  on 
the  leaves.  The  series  of  cell-like  holes  or  chain-like  markings 
which  it  makes  in  the  leaves  are  usually  the  first  thing  to 
attract  the  attention  of  the  grower  to  the  fact  that  these  little 
pests  are  in  his  vineyard.  The  young  larvae  which  hatch  from 
the  eggs,  that  are  deposited  on  the  inner  bark  or  in  crevices  of 
the  vine,  make  their  way  into  the  ground  and  begin  feeding  on 
the  roots.  If  they  are  abundant  they  may  destroy  many  of  the 


466    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

smaller  rootlets  and  may  even  injure  the  larger  roots  by  eating 
off  the  bark.  They  lie  dormant  during  the  winter,  and  come 
near  the  surface  early  in  the  spring  to  pupate. 

Deep  cultivation  late  in  the  fall  or  early  in  the  spring  will 
destroy  many  of  the  larvae  and  pupae.  A  thorough  spraying 
with  arsenate  of  lead  as  soon  as  the  beetles  appear  will  destroy 
many  of  them,  but  a  second  spraying  may  be  necessary  a  little 
later. 

The  Imported  Grape-root  Worm  (Adoxus  mtis),  which  occurs 
in  California,  has  habits  similar  to  the  eastern  species  just 
described,  and  yields  to  the  same  treatment. 

The  Grape-vine  Flea-beetles  (Haltica  spp.). — These  are 
small,  shining,  green  or  dark  blue  beetles,  characterized  by  their 
strongly  developed  hind  legs  which  enable  them  to  leap  for 
considerable  distances.  The  rose-chafer,  Macrodactylus  sub- 
spinosus,  slender  bodied  and  with  long  slender  spiny  legs,  is 
another  beetle  that  feeds  on  the  foliage  of  the  grape.  In  spray- 
ing for  these  various  beetles  the  work  must  be  done  early,  and 
it  is  often  advisable  to  add  glucose  or  molasses  to  the  arsenate 
of  lead  (see  page  415.) 

The  Grape-berry  Moth  (Polychrosis  viteana),  and  the  grape 
curculio,  Capronius  inaqualis,  the  larvae  of  both  of  which  feed 
on  the  foliage  but  do  more  damage  by  attacking  the  fruits,  may 
be  controlled  by  similar  arsenical  sprays. 

The  Grape  Leaf -hopper  (Typhlocyba  comes). — This  is  a  very 
widely  distributed  pest  of  the  vines,  and  has  come  to  be  known 
by  many  common  names,  such  as  leaf-hopper,  vine-hopper, 
vine-thrips  or  thrips,  but  as  it  is  not  a  thrips  at  all,  and  as  there 
are  several  other  kinds  of  leaf-hoppers,  it  is  better  to  call  it  the 
grape  leaf-hopper.  The  adults  are  about  one-eighth  of  an  inch 
long,  with  the  body  and  wings  prettily  marked  with  red  or 
yellowish  bands  or  spots.  The  over-wintering  adults  appear 
on  the  vines  as  soon  as  the  buds  open,  and  a  little  later  lay  their 
eggs  beneath  the  epidermis  of  the  underside  of  the  leaf.  The 
young  are  small,  whitish,  wingless  insects  with  conspicuous 
red  eyes,  but  become  more  and  more  like  the  adult  with  each 
molt.  In  some  regions  there  is  only  one  generation  each  year, 
but  in  other  places  there  may  be  a  partial  or  even  a  full  second 


INSECTS  INJURIOUS  TO  BERRIES  467 

generation.  Adults  hibernate  in  leaves  or  rubbish  in  the  vine- 
yard or  along  the  fences  or  in  near-by  fields  or  meadows,  and  if 
such  places  are  burned  over  during  late  fall  or  winter  these 
hibernating  adults  may  be  destroyed. 

When  the  insects  attack  the  vines  they  may  be  more  or 
less  successfully  controlled  by  spraying  with  some  contact 
insecticide,  such  as  whale-oil  soap,  kerosene  emulsion,  or 
resin  spray  (see  page  417).  An  undershot  nozzle  must  be 
used  and  great  care  taken  to  reach  the  underside  of  all  the 
leaves.  In  California  and  other  places  where  the  vines  are 
pruned  back  close  to  the  main  trunk  each  year,  a  hopper  cage 
made  by  fastening  fine  wire  screen,  such  as  mosquito  netting, 
over  a  frame  may  often  be  used  with 
success.  One  side  of  the  cage  is  left 
open  and  the  bottom  is  made  of  a 
shallow  tray  with  a  U-shaped  opening 
so  that  the  cage  may  be  pushed  over 
the  vine.  The  sides  of  the  tray  are 
smeared  with  crude  oil  so  that  the 
hoppers  that  fly  from  the  vine  when  FlG  22I._Grape  leaf- 
it  is  jarred  are  caught  and  killed  in  hoppers,  at  left  Typhlocyba 
this  material.  When  the  vines  are  v^erata,  on  right  T  comes. 
,  ,  ,  e  ...  (Much  enlarged:  after 

not  pruned  back,  of  course,  this  cage    Forbes.) 

cannot  be  used.     In  such  places  sticky 

shields  against  which  the  leaf-hoppers  are  likely  to  jump  when 
two  men  are  carrying  them  on  opposite  sides  of  the  vines,  may 
catch  and  destroy  large  numbers  of  these  pests. 


RASPBERRIES  AND  BLACKBERRIES 

The  most  serious  pests  of  raspberries  and  blackberries  are  the 
borers  that  attack  the  canes.  The  raspberry  root-borer,  Bem- 
becia  marginata,  also  called  the  raspberry  crown-borer,  usually 
attacks  the  plant  below  the  surface  of  the  ground,  sometimes 
girdling  and  killing  it,  but  it  may  sometimes  leave  the  roots 
and  bore  into  the  canes.  The  adult  insects  are  beautiful  clear- 
winged  moths  related  to  the  peach-tree  borer  and  the 


468    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 


currant-borers.      The  aflected  plants  should  be  dug  up  and 
burned. 

The  Raspberry  Cane-borer  (Oberea  bimaculata) ,  the  adult  of 
which  is  a  slender  cylindrical  beetle  about  one-half  an  inch 
long  with  antennae  about  as  long  as  the  body,  and  the  red- 
necked cane-borer,  Agrilus  ruficollis,  the  larvae  of  a  flat  blackish 
or  bronze-colored  beetle  with  a  red  prothorax,  both  attack 
the  canes  of  raspberries  and  blackberries.  The  larvae  of  a 
fly  that  looks  very  much  like  a  small  house-fly  also  often 
destroy  many  of  the  new  shoots. 

In  all  these  cases  affected  canes  should 
be  cut  out  and  destroyed  as  soon  as  no- 
ticed. 

Scale-insects. — Among  the  scale-insects 
which  often  attack  the  raspberry  and 
blackberry  vines,  the  rose-scale,  Aulacaspis 
rosce,  is  perhaps  the  most  common.  Atten- 
tion is  usually  attracted  to  the  presence  of 
this  insect  by  the  white  elongate  scales  of 
the  males  which  often  occur  in  such  num- 
bers as  to  make  the  canes  look  as  if  they 
had  been  whitewashed.  The  scale  of  the 
female  is  circular  and  somewhat  darker. 

The  badly  infested  canes  should  be  cut 
out  and  the  others  sprayed  with  the  sul- 
phur-lime wash  during  the  winter. 

Such  leaf-feeding  insects  as  the  raspberry 
sa,w-fty,Monophadnoidesrubi,  and  the  rasp- 
berry Byturus,  Byturus  ttnicolor,  may  be 
controlled  by  spraying  with  arsenate  of 
lead,  if  the  application  is  made  before  the 
berries  form.  If  the  slug-like  larvae  of  saw-flies  appear  later, 
white  hellebore  may  be  sprayed  or  dusted  on  the  plants.  A 
little  greenish  or  brownish  mite,  Bryobia  pratensis,  referred 
to  on  page  212,  often  occurs  in  destructive  numbers  on  the 
raspberry  leaves  causing  them  to  turn  yellow  and  fall. 
Thorough  sprayings  or  dustings  with  sulphur  will  usually 
control  them. 


FIG.  222. —  Rose 
scale,  Aulacaspis 
rosa,  on  blackberry 
bush.  (About  nat- 
ural size.) 


INSECTS  INJURIOUS  TO  BERRIES 


469 


CURRANTS  AND  GOOSEBERRIES 

As  with  the  raspberries  and  blackberries  the  cane-borers  are 
the  most  important  enemies  of  the  currant  and  gooseberry 
bushes. 

The  Imported  Currant-borer  (JEgeria  tipuliformis}. — In 
appearance  and  habits  this  insect  is  much  like  the  raspberry 
root-borer,  but  it  works  in  the  canes  above  the  ground  and 
not  in  the  crown  or  roots.  The  eggs  are  laid  in  the  axils  of 
the  leaves  or  on  the  currant  canes,  the  larvae  boring  into  the 
canes  as  soon  as  they  are  hatched.  During  the  winter  the 
half-grown  larvae  may  be  found  in  the  center  of  the  cane  at 
the  bottom  of  the  burrow  where 
they  have  been  working.  Early 
in  the  spring  they  commence  to 
work  again,  pupating  in  May. 
The  adult  moths  issue  in  June. 

The  leaves  of  the  affected  canes 
are  lighter  or  yellowish  in  color, 
thus  enabling  one  to  detect  and 
prune  out  the  affected  parts  of 
the  bush.  All  dead  or  affected 
wood  should  be  cut  out  and  de- 
stroyed as  early  as  possible. 

The  Currant-stem  Girdler 

(J anus  integer] . — This  is  a  small,  slender,  shining  black  saw- 
fly  that  girdles  the  currant  canes  just  above  the  point  where 
she  lays  her  eggs. 

As  the  first  indication  of  the  presence  of  the  pest  is  the 
dying  tips  that  have  been  girdled,  nothing  can  be  done  to  check 
the  damage  that  season,  but  if  the  affected  stalks  are  cut  off 
three  or  four  inches  below  where  they  were  girdled  the  larvae, 
which  are  lying  in  the  stalks,  may  be  destroyed.  If  the  prun- 
ing is  left  until  winter  time  the  cut  should  be  made  eight  or 
nine  inches  below  the  dead  end  of  the  cane. 

The  Currant  Saw-flies  (Pteronus  ribesi  and  Gymnonychus 
appendiculatus). — 'The  larvae  of  these  saw-flies,  which  feed  on  the 
foliage,  and  any  other  leaf-feeding  larvae  may  be  controlled  by 


FIG.  223. — Imported  currant- 
borer,  Mgeria  tipuliformis, 
adult.  (About  natural  size.) 


470    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

spraying  with  arsenate  of  lead  while  there  is  no  fruit  on  the 
bushes.  At  other  times  white  hellebore  should  be  dusted 
or  sprayed  over  the  plants. 

The  Currant  Aphis  (Myzus  ribis}. — In  the  spring  or  early 
summer  the  leaves  of  the  currant  bushes,  and  less  frequently 
the  gooseberry  bushes,  become  more  or  less  blistered  and  swollen 
and  curled.  The  distorted  parts  are  usually  conspicuously 
red  in  color  and  soon  attract  attention.  Examination  will 
reveal  colonies  of  small  yellowish-green  aphids  on  the  under- 
side of  the  leaves. 

When  only  a  few  of  the  leaves  are  affected  they  should  be 
picked  off  and  destroyed.  Spraying  with  kerosene  emulsion 
or  whale-oil  soap  or  tobacco  extract  is  effective  if  care  is  taken 
to  reach  the  aphids  before  they  have  become  well  protected 
by  the  curling  of  the  leaves.  If  the  bushes  are  sprayed  during 
the  winter  with  sulphur-lime  solution  many  of  the  eggs  will  be 
destroyed. 

Scale -insects. — Several  different  species  of  scale-insects,  the 
most  important  of  which  is  the  San  Jose  scale  (see  page  445), 
often  attack  the  currant  and  gooseberry  bushes  and  sometimes 
prove  very  destructive.  The  best  remedy  is  to  prune  out  the 
parts  that  are  badly  infested  and  spray  the  rest  with  sulphur- 
lime  solution  during  the  winter. 

The  Yellow  Currant-fly  (Epochra  canadensis}. — This  fly  is 
about  the  size  of  the  house-fly,  but  the  body  is  more  slender 
and  the  wings  are  longer  and  narrower.  The  body  and  legs 
are  pale  yellow  or  brownish  and  the  wings  are  marked  with 
brownish  cross  bands.  This  insect  passes  the  winter  in  the 
pupal  stage  in  the  ground  or  in  rubbish  below  the  bushes. 
The  flies  issue  early  in  the  spring  and  the  females  deposit 
their  eggs  in  the  berries  just  underneath  the  skin.  The  larvae 
feed  upon  the  pulp  and  seeds,  and  when  full  grown  they  leave 
the  berries,  which  have  dropped  to  the  ground,  and  enter 
the  ground  to  pupate.  These  fallen  berries  should,  if  possible, 
be  destroyed  before  the  larva?  leave  them.  If  chickens  are 
allowed  to  run  under  the  bushes  they  will  pick  up  many  of 
the  larvaa  and  pupa3.  An  effective  but  rather  expensive  way  to 
save  the  crop  of  berries  is  to  cover  the  entire  bush  with  mosquito 


INSECTS  INJURIOUS  TO  BERRIES 


netting  taking  care  to  tie  it  carefully  around  the  bottom.  If 
this  is  done  just  after  the  berries  have  formed,  and  before  the 
flies  appear,  none  of  the  berries  can  become  infested. 

A  radical  remedy  is  to  destroy  all  of  the  fruit  while  it  is 
quite  small  before  any  of  the  larvae  have  had  a  chance  to  pupate. 
Thus  by  the  loss  of  one  crop  all  the  flies  in  the  garden  will  be 
destroyed,  and  reinfestation  can  only  come  from  a  neighbor's 
field.  As  the  flies  do  not  often  fly  far  from  the  bushes  this  in- 
festation will  come  but  slowly. 


FIG.  224. — Yellow  currant-fly,  Epochra  canadensis,  laying  eggs  on  currants 
(Somewhat  enlarged;  photo  by  Paine.) 

The  Dark  Currant-fly  (Rhagoletis  ribicola). — This  fly  is  not 
as  well  known  as  the  preceding  species,  but  in  the  state  of 
Washington  and  other  places  it  is  often  very  abundant  and 
destructive.  The  adult  is  only  about  half  as  large  as  a  house- 
fly. The  body  is  shining  black,  the  thorax  marked  by  four 
narrow  yellow  lines  and  a  conspicuous  yellow  spot.  The 
wings  are  marked  with  four  broad,  brown  cross  bands,  the 
outer  pair  of  which  are  united  anteriorly.  The  habits  are 
similar  to  those  of  the  preceding  species,  and  the  control 
measures  the  same. 


472     ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

STRAWBERRIES 

The  Strawberry  Crown-borer  (Tyloderma  jr  agarics). — The 
white  grub-like  larvae  of  this  beetle  often  cause  the  death  of 
many  plants  by  boring  into  the  crown  and  eating  out  a  large 
cavity.  The  dark-colored  adult  is  about  one-fifth  of  an  inch 
long,  and  belongs  to  the  group  of  snout  beetles,  having  the  head 
produced  into  a  conspicuous  blunt  snout.  The  beetles  pass  the 


FIG.  225. — Larvas  of  strawberry  crown-moth,  Sesia  niiilans,  in  crown  of 
strawberry  plant.     (Somewhat  reduced.) 

winter  in  the  soil,  emerging  in  the  spring  to  lay  their  eggs  on 
the  plants.  All  dead  or  weakened  plants  should  be  dug  out  and 
destroyed  as  soon  as  noticed.  As  soon  as  a  bed  becomes 
badly  infested  it  should  be  plowed  up  and  a  new  one  planted 
elsewhere,  care  being  taken  to  use  young  plants  that  contain 
no  eggs  or  larvae  of  this  pest.  As  the  beetles  cannot  fly  the  new 
bed  will  not  be  readily  infested. 


INSECTS  INJURIOUS  TO  BERRIES  473 

The  Strawberry  Crown-moth  (Sesia  rutilans).— On  the 
Pacific  Coast  the  strawberry  crown-borer  does  not  occur,  but 
in  its  stead  is  another  pest  that  works  in  much  the  same  way 
and  is  even  more  destructive.  This  is  called  the  strawberry 
crown-moth.  The  moths  are  a  beautiful  steel-blue  or  black. 
The  adults  lay  their  eggs  on  the  crown  of  the  plant  early  in 
the  summer,  and  as  the  larvae  develop  they  bore  deeper  and 
deeper  into  the  crown  of  the  plant,  sometimes  penetrating 
the  larger  roots.  They  may  feed  on  the  plants  all  winter, 
changing  to  the  pupae  early  in  the  summer. 

The  control  measures  suggested  for  the  preceding  species 
should  be  used  in  fighting  this  insect.  Care  must  be  taken 
to  remove  all  of  the  crown  and  the  large  roots,  or  the  larvae 
will  be  left  in  the  ground. 

The  Strawberry  Weevil  (Anthonomus  signatus). — These 
little  snout  beetles  appear  in  the  strawberry  patch  early  in  the 
spring  and  gnaw  small  holes  through  the  outer  crust  of  the 
nearly  mature  buds  where  they  deposit  their  eggs.  They  then 
cut  the  stem  so  that  the  bud  soon  falls  to  the  ground.  Where 
this  pest  is  bad,  only  enough  of  the  staminate  varieties  of 
vines  should  be  grown  to  insure  good  fertilization,  as  the 
larvae  feed  on  the  pollen  of  these  plants.  It  may  even  prove 
profitable  in  some  instances  to  plant  early  blooming  staminate 
varieties  in  places  where  the  beetles  may  readily  gain  access 
to  them,  and  then  destroy  the  plants  after  the  beetles  have 
laid  all  their  eggs  and  before  the  adults  of  the  next  generation 
issue.  Clean  culture  is  important  in  order  that  the  beetles 
may  have  few  places  in  which  to  hibernate. 

Strawberry  Root-worms. — The  larvae  of  three  or  more  species 
of  beetles  may  be  found  on  the  roots  of  the  strawberries,  some- 
times entering  the  crown  also.  The  adult  beetles  are  leaf 
feeders,  and  may  be  controlled  by  spraying  with  arsenate  of 
lead.  Where  the  roots  are  badly  infested  they  should  be  dug 
out  and  burned. 

The  Strawberry  Root-louse  (Aphis  forbesi). — Early  in  the 
spring  a  few  small  greenish  aphids  may  be  found  on  the 
underside  of  the  strawberry  leaves.  Late  in  April  or  early  in 
June  ants  begin  to  appear  on  the  vines  in  considerable  numbers, 


474    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  soon  after  this,  if  the  roots  of  the  plants  are  examined,  the 
aphids  will  be  found  there  also.  The  ants  have  carried  the 
aphids  from  their  nests  to  the  roots,  where  they  continue  to 
care  for  them,  taking  them  to  new  plants  when  the  old  plants 
die  or  become  overcrowded.  During  the  summer  winged 
generations  of  the  aphids  appear,  and  thus  distribute  the  species 
over  wider  areas.  Late  in  the  fall  the  winged  sexual  generation 
occurs,  and  the  eggs  are  laid  on  the  underside  of  the  leaves, 
where  they  remain  until  they  hatch  in  the  following  spring. 
Little  can  be  done  to  control  the  aphids  on  the  roots  of  the 
plants.  If  the  bed  is  badly  infested  the  vines  should  be  lightly 
covered  with  straw  early  in  the  spring  and  the  whole  area 
burned  over.  This  will  burn  all  the  leaves  and  stems  and 
destroy  all  the  aphids  as  well  as  many  other  insects.  A  quick, 
hot  fire  will  not  seriously  injure  the  plants.  Care  should  be 
taken  in  selecting  plants  for  transplanting  to  see  that  there  are 
no  eggs  on  the  leaves  nor  aphids  on  the  roots. 


CHAPTER  XXXV 
INSECTS  INJURIOUS  TO  GARDEN  TRUCK 

Only  the  market  gardener  and  those  who  have  tried  to  raise 
a  few  vegetables  in  their  own  kitchen  gardens  realize  how  many 
and  how  vexing  are  the  insect  pests  of  garden  truck.  The  an- 
nual value  of  the  truck  crops  in  the  United  States  is  estimated 
to  be  more  than  three  hundred  million  dollars,  and  yet  each 
year  the  insects  take  about  one-fifth  of  the  vegetable  crops, 
causing  a  loss,  therefore,  of  more  than  sixty  million  dollars. 

The  garden  pests,  like  those  of  the  orchards  and  grain  fields, 
are  various  in  kind  and  life-history  and  in  the  manner  in  which 
they  work  their  injuries.  Leaf-eating  beetles  are  especially 
numerous  and  serious  in  their  attacks.  The  black  and  yellow 
striped  Colorado  potato-beetle,  the  active,  leaping,  little  flea- 
beetles  and  the  spotted  and  striped  Diabroticas  are  conspicuous 
and  familiar  examples  of  these  leaf-eaters.  The  caterpillars 
of  various  moths  and  butterflies  also  strip  or  mutilate  the 
leaves  of  many  vegetables.  Cut-worms  and  army-worms  are 
notorious  pests  of  this  kind.  The  naked  green  cabbage-worm, 
which  is  the  larva  of  a  dainty  white  butterfly  imported  from 
Europe  half  a  century  ago,  is  an  especially  serious  caterpillar 
enemy  of  cabbages  and  other  cruciferous  garden  plants.  Several 
species  of  aphids  often  occur  in  sufficient  numbers  to  do  serious 
damage  to  peas,  beets,  cabbages  and  other  vegetables.  Squash- 
bugs,  the  harlequin  cabbage-bugs,  certain  leaf-hoppers  and 
other  sucking  bugs  of  the  order  Hemiptera  take  a  heavy  toll 
of  plant  sap  from  many  garden  plants. 

The  remedies  for  garden  pests  have  to  be,  like  those  for  the 
pests  of  vineyards  and  berries,  especially  devised  to  fit  the 
particular  conditions  of  vegetable  growing.  Not  many  kinds 
of  garden  truck  can  be  sprayed  with  arsenical  poisons,  although 
some,  of  course,  notably  potato  plants,  can.  Such  simple 

475 


476    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

but  often  sufficient  means  as  hand-picking  and  trapping  can  be 
effectually  used,  especially  in  smaller  gardens.  Clean  cultiva- 
tion and  the  destroying  of  all  hiding,  places  for  over- wintering 
insects  are  great  helps  in  the  struggle. 

Various  special  remedies  are  described  in  the  accounts,  which 
follow,  of  a  few  of  the  more  important  of  the  garden  truck 
pests. 

POTATOES 

The  Colorado  Potato -beetle  (Leptinotarsa  decemlineata). — 
This  beetle  is  in  many  regions  the  best  known  of  all  the  garden 
pests.  Its  black  and  yellowish  striped  wings  make  it  a 


FIG.  226. — Colorado   potato-beetle,    Leptinotarsa  decemlineata,   and    its 
larva.     (About  twice  natural  size.) 

conspicuous  object  on  the  vines,  and  the  results  of  its  work  are 
all  too  evident.  It  furnishes  a  good  example  of  the  way  in 
which  an  insect  once  regarded  as  harmless  may,  by  a  slight 
change  in  its  habits,  become  of  very  great  economic  im- 
portance. Originally  it  fed  on  various  common  weeds,  es- 
pecially the  Colorado  thistle,  Solanum  rostratum,  in  Colorado 
and  other  Rocky  Mountain  states.  When  potatoes  (another 
species  of  Solanum)  began  to  be  planted  in  the  region  where 
the  beetle  occurred  it  found  them  more  to  its  liking,  and  with 
the  abundance  of  food  that  could  be  had  with  little  or  no  effort, 
it  so  increased  in  numbers  and  spread  so  rapidly  that  it  soon 


INSECTS  INJURIOUS  TO  GARDEN  TRUCK    477 

became  a  most  formidable  foe,  whose  destructive  work  was 
checked  only  when  we  learned  to  use  Paris  green. 

The  beetles  pass  the  winter  in  the  ground,  appearing  in  the 
spring  as  soon  as  the  potatoes  begin  to  grow.  When  the  insects 
are  abundant  they  may  entirely  destroy  the  young  plants. 
The  eggs  are  laid  on  the  leaves,  and  the  larvae,  which  appear  a 
little  later,  also  attack  the  plants.  There  may  be  two  or  even 
three  generations  during  the  year.  The  insect  has  many  ene- 
mies, the  most  important  of  which  are  certain  tachina-flies, 
which  lay  their  eggs  on  the  larvae,  and  certain  predaceous  insects 
which  feed  on  the  eggs  or  larvae.  In  small  patches  the  beetles, 
larvae  and  eggs  may  be  gathered  from  the  vines  and  destroyed. 
Larger  areas  should  be  sprayed  with  Paris  green  or  arsenate  of 
lead,  most  growers  now  preferring  the  latter.  It  is  used  at  the 
rate  of  three  to  five  pounds  to  fifty  gallons  of  water,  the  stronger 
spray  being  used  for  the  beetles,  the  weaker  for  the  larvae. 

Flea-beetles  (Epitrix  spp). — There  are  several  species  of 
flea-beetles  that  occur  in  the  garden,  attacking  almost  all  kinds 
of  plants.  These  are  all  small  dark  beetles  that  leap  quickly 
when  disturbed.  They  pass  the  winter  in  leaves  or  rubbish 
in  the  garden  or  along  the  fences,  and  early  in  the  spring  attack 
the  young  plants  as  soon  as  they  appear  above  the  ground. 
Particular  damage  may  be  done  to  potatoes  by  the  minute 
whitish  larvae  which  sometimes  feed  on  the  tubers,  making 
discolored  little  holes  in  them  that  detract  from  their  market 
value. 

If  the  plants  are  thoroughly  sprayed  very  early  with  arsenate 
of  lead  most  of  the  beetles  may  be  destroyed.  Bordeaux  mix- 
ture seems  to  act  as  a  repellent,  so  it  is  often  worth  while  to  use 
it  and  lead  arsenate  combined.  When  the  tubers  are  infested 
by  the  larvae  they  should  be  dug  up  as  soon  as  they  are  mature 
and  exposed  to  the  sun  for  a  few  hours  before  storing. 

Potato  Stalk-borer  (Trichobaris  trinotata) . — This  is  a  small 
whitish  grub  that  bores  into  the  potato  stalks,  weakening  or 
entirely  destroying  them.  The  pupa  is  formed  in  the  vine 
near  the  surface  of  the  ground,  and  the  small  grayish  snout 
beetle,  which  issues  a  little  later,  remains  there  all  winter.  This 
suggests  an  efficient  remedy.  The  vines  should  be  raked  up 


478    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  burned  as  soon  as  the  potatoes  are  dug.  These  beetles 
feed  on  several  different  kinds  of  weeds  so  that  any  weeds 
in  and  near  the  garden  should  also  be  destroyed. 

There  is  also  another  borer,  the  larva  of  the  moth  Papaipema 
nitella,  that  attacks  potato  stalks  as  well  as  tomatoes,  corn, 
and  many  other  plants.  The  larva?  pupate  in  the  lower 
part  of  the  stalk;  therefore  if  the  old  vines  and  weeds  are 
destroyed  early  in  the  fall  this  pest  will  usually  not  become 
troublesome. 

The  Potato  Tuber-worm  (Phthorimcea  operculella). — For  a 
long  while  this  has  been  the  most  serious  pest  of  potatoes  in 
California.  In  the  southern  states  it  is  a  common  tobacco  pest, 
and  has  recently  been  reported  as  injuring  potatoes  there  also. 
The  moth  issues  early  in  the  spring  and  lays  her  eggs  on  the 
young  potato  plants.  The  larvae  bore  into  the  stalks,  often 
killing  them,  but  most  damage  is  done  when  they  make  their 
way  into  the  ground  and  attack  the  tubers,  boring  irregular 
channels  in  them  and  soon  rendering  the  potatoes  unfit  for  use. 
Several  generations  may  occur  each  season,  the  moths  of  the 
later  broods  laying  their  eggs  on  the  tubers  when  opportunity 
offers. 

When  plants  are  found  to  be  wilting  on  account  of  the 
presence  of  these  larvae  in  the  stalks  they  should  be  cut  and 
destroyed  to  prevent  infestation  by  later  broods.  The  field 
and  adjoining  lands  should  be  kept  free  of  nightshade  and 
other  related  plants  as  this  insect  feeds  on  these  also.  The 
potatoes  should  be  exposed  as  little  as  possible,  both  before  and 
after  digging,  so  that  the  moth  may  not  have  an  opportunity 
to  lay  her  eggs  on  them.  If  stored  potatoes  are  found  to  be 
badly  infested  they  may  be  fumigated  with  carbon  bisulphide. 
Four  or  more  treatments  at  short  intervals  may  be  necessary 
before  all  of  the  larvae  are  destroyed. 

PEAS  AND  BEANS 

The  Pea -weevil  (Bruchus  pisorum). — This  common  and 
widespread  pest  has  made  it  impracticable  to  grow  peas  on  a 
large  scale  in  many  regions.  Some  parts  of  Canada  and  some 


INSECTS  INJURIOUS  TO  GARDEN  TRUCK    479 

of  the  northern  states  are  comparatively  free  from  the  pest, 
and  so  furnish  most  of  the  seed  that  is  used.  The  adults,  which 
are  small,  grayish,  snouted  beetles,  appear  on  the  vines  while  the 
peas  are  in  blossom,  and  lay  their  eggs  on  the  young  pods. 
The  larvae  enter  and  feed  on  the  peas,  finally  pupating  in  them. 
In  the  northern  regions  they  remain  in  the  seed  until  it  is 
planted  the  following  spring.  In  other  places  they  leave  the 
peas  in  the  fall. 

As  there  is  only  one  generation  a  year,  and  as  this  species 
does  riot  breed  in  dry  peas,  it  is  often  worth  while  to  hold  the 
seed  in  bins  or  sacks  until  all  of  the  adults  have  issued.  Or  the 


FIG.  227. — Pea-weevils,   Bruchus  pisorum,  and  infested    peas.      (About 
twice  natural  size.) 

seed  may  be  treated  by  heating  or  scalding  or  fumigating  with 
carbon  bisulphide. 

The  Bean -weevil  (Bruchus  oUectus). — This  is  the  most 
common  of  three  or  four  species  of  bean-weevils  that  occur  in 
some  parts  of  the  United  States.  The  adults  are  only  about 
one-eighth  of  an  inch  long,  dark-colored  and  short-snouted. 
Several  larvae  or  bettles  may  be  found  in  one  bean,  and  they 
continue  to  breed  in  the  stored  product  throughout  the  year. 
All  infested  beans  should  be  fumigated  with  carbon  bisulphide 
as  soon  as  possible.  If  the  seed  is  thrown  lightly  into  water 
most  of  the  infested  beans  will  float.  By  destroying  these  one 
can  avoid  planting  infested  seed. 


480    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  Pea  Aphis  (Macrosiphum  pisf). — This  large  green  aphis 
sometimes  appears  on  the  peas  in  such  numbers  as  to  weaken 
very  much  or  even  to  kill  the  plants.  The  insects  pass  the 
winter  on  clover  and  vetches,  sometimes  doing  considerable 
injury  to  these  plants.  They  are  usually  fairly  well  controlled 
by  natural  enemies  and  fungus  diseases,  but  it  is  sometimes 
necessary  to  resort  to  spraying  in  order  to  save  the  crop. 
Whale-oil  soap  or  some  of  the  tobacco  washes  may  be  used. 
Considerable  force  must  be  used  in  applying  the  spray.  It  is 
sometimes  practicable  to  brush  the  aphids  from  the  vines  and 
destroy  them  by  covering  them  with  soil.  Clover  and  peas 
should  not  be  planted  close  together. 

The  Bean  Thrips  (Heliothrips  fasciatus) . — In  many  places  on 
the  Pacific  coast  this  is  the  most  serious  pest  of  the  peas  and 
beans.  It  also  does  a  great  deal  of  damage  to  tomatoes,  po- 
tatoes, alfalfa  and  many  other  cultivated  and  wild  plants. 
The  black-bodied  little  insect,  with  its  four  narrow,  hair- 
fringed  wings,  is  so  small  that  it  rarely  attracts  attention  even 
when  present  in  great  numbers,  and  its  presence  is  usually 
not  suspected  until  the  leaves  of  the  plant  begin  to  turn  yellow- 
ish and  dry  up  because  the  sap  has  been  sucked  out.  There 
are  six  or  seven  generations  during  the  year.  The  young 
are  wingless  and  whitish,  often  with  reddish  markings  on  the 
sides  of  the  body. 

Because  the  insect  feeds  more  commonly  on  the  underside  of 
the  leaves,  and  on  account  of  the  nature  of  the  crops  that  it 
infests,  it  is  rarely  practicable  to  control  this  pest  by  spraying. 
We  must  depend,  then,  upon  the  natural  enemies  of  the  thrips, 
and  clean  culture  methods,  for  control.  As  this  thrips  feeds 
on  many  weeds,  particularly  on  wild  lettuce,  these  should  be 
kept  out  of  the  garden  and  nearby  fields. 

CABBAGE 

The  Imported  Cabbage-worm  (Pontia  rapes). — This  is  the 
most  common  of  a  number  of  butterfly  and  moth  larvse  that 
feed  on  cabbage.  Before  this  species  was  introduced  into 
America,  more  than  fifty  years  ago,  the  larvae  of  some  of  our 
native  butterflies  belonging  to  the  same  genus  were  often 


INSECTS  INJURIOUS  TO  GARDEN  TRUCK    481 

abundant  in  gardens,  but  they  did  not  bore  into  the  head  of 
the  cabbage  as  the  invader  does,  and  so  were  not  such  serious 
pests.  Because  it  breeds  more  prolifically  and  feeds  earlier 
and  later  in  the  season  the  imported  species  has  almost  or  quite 
driven  the  others  from  the  garden.  The  familiar  white  cab- 
bage-butterflies, with  their  black-tipped  fore  wings,  appear 
early  in  the  spring  and  lay  their  eggs  on  almost  any  available 


FIG.  228. — The  imported  cabbage-butterfly,  Pontia  raps;  male   above, 
female  below.     (Natural  size.) 

food.  In  the  south  the  adults  may  be  found  at  all  times  of  the 
year.  The  female  has  two  black  spots  in  the  disc  of  each  fore 
wing,the  male  only  one.  Both  sexes  have  a  spot  on  the  anter- 
ior margin  of  the  hind  wing.  The  larvae  are  velvety  green 
with  a  faint  yellowish  line  above  and  yellowish  spots  on  the 
sides.  The  pupae,  or  chrysalids,  are  usually  found  on  the 
underside  of  leaves,  on  rocks,  fences  or  other  objects.  The  insect 
usually  passes  the  winter  in  the  field  in  the  pupal  stage. 


482    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Minute  hymenopterous  parasites  and  other  enemies  aid  in 
controlling  this  pest,  but  it  is  sometimes  necessary  to  spray 
with  arsenate  of  lead,  two  or  three  pounds  to  thirty  gallons  of 
water.  Where  the  insect  is  troublesome  the  spraying  should  be 
done  early  and  repeated  as  often  as  is  necessary  to  protect  the 
plants  until  the  heads  form.  If  the  fields  are  well  cleaned  many 
of  the  over-wintering  pupse  will  be  destroyed.  The  same  meas- 
ures should  be  used  for  the  control  of  any  of  the  other  leaf- 
feeding  larvae,  and  for  the  flea-beetles  and  others  that  often 
attack  the  cabbage. 

The  Harlequin  Cabbage -bug  (Murgantia  histrionica). — 
These  bright-colored  cabbage-bugs,  or  calico-backs,  or  fire- 
bugs, are  often  found  feeding  on  the  cabbage,  where  they  do 
much  damage,  particularly  to  young  plants,  by  sucking  the 
sap  from  them.  The  adults,  which  hibernate  in  rubbish,  be- 
come active  very  early  in  the  spring.  This  has  suggested  the 
use  of  trap-crops  such  as  kale,  which  may  be  planted  early  so 
that  the  bugs  may  feed  on  it  and  be  destroyed  there  by  spray- 
ing with  kerosene  before  the  cabbages  are  planted.  The  young, 
or  nymphs,  may  be  destroyed  on  the  cabbage  by  spraying  with 
strong  kerosene  emulsion  or  whale-oil  soap.  If  a  field  is  kept 
clean  during  the  winter,  so  that  the  insects  will  have  few  places 
in  which  to  hibernate,  they  will  usually  not  become  destruc- 
tively abundant. 

The  Cabbage  Aphis  (Aphis  brassica). — These  little  green- 
ish aphids  are  nearly  always  more  or  less  abundant  on  the 
cabbage,  but  usually  little  damage  is  done  except  to  the 
young  plants.  Any  of  the  contact  insecticides,  such  as  kero- 
sene emulsion,  or  whale-oil  soap,  or  tobacco  extract,  will 
destroy  the  aphids  if  it  is  applied  with  considerable  force. 
Again,  clean  culture  is  the  most  successful  means  for  combat- 
ting this  garden  pest,  for  if  all  of  the  refuse  is  destroyed  in  the 
field  the  over-wintering  insects  will  perish 

The  Cabbage -maggot  (Pegomyia  brassicce). — The  roots  of 
cabbage,  cauliflower  and  radishes  are  frequently  tunneled  by 
small  whitish,  footless  maggots  which  are  sometimes  so  numer- 
ous that  they  seriously  weaken  or  kill  the  plant.  The  adults 
are  small  flies  that  look  much  like  the  common  house-fly,  but 


INSECTS  INJURIOUS  TO  GARDEN  TRUCK    483 

they  are  less  than  one-fourth  of  an  inch  long.  The  flies  lay 
their  eggs  on  the  plant  close  to  the  surface  of  the  ground,  or 
in  the  soil  near  the  plant.  The  larvae  soon  mine  into  the 
stalk  or  roots,  where  they  feed  for  a  few  weeks,  entering  the 
soil  again  to  pupate.  There  may  be  two  or  three  generations 
during  the  summer. 

After  the  larvae  have  entered  the  plant  but  little  can  be  done 
to  control  them.  Most  of  them  can  be  killed  by  pouring  a 
teaspoonful  of  carbon  bisulphide  in  a  small  hole  four  or  five 
inches  from  the  plant,  but  this  is  hardly  practicable  on  a  large 
scale.  Control  by  cultural  methods  is  more  satisfactory.  All 
the  old  plants  and  roots  should  be  destroyed  early  in  the  fall, 
as  many  of  the  pupae  pass  the  winter  in  or  around  these.  Fall 
plowing  and  crop  rotation  are  to  be  recommended.  Mustard 
and  other  cruciferous  wild  plants  should  not  be  allowed  in  or 
near  the  garden,  as  they  also  harbor  this  pest.  If  the  cabbages 
are  not  planted  until  most  of  the  flies  have  laid  their  eggs  on  some 
other  plants  they  will  escape  serious  injury.  Seed  beds  should 
be  protected  so  the  plants  will  not  become  infected  before  they 
are  transplanted.  Some  growers  keep  the  fly  from  laying  her 
eggs  on  the  plant  by  protecting  it  with  a  collar  of  tarred  felt 
paper  which  lies  on  the  ground  and  surrounds  the  base  of  the 
plant.  Gas  tar  and  other  repellents  have  been  used  with  more 
or  less  success.  Very  early  or  very  late  radishes  may  escape 
infestation. 

BEETS 

The  Beet  Leaf -hopper  (Eutettix  tenella). — In  some  of  the 
western  states  where  sugar  beets  are  grown  extensively  a 
condition  known  as  beet  curly-leaf,  or  blight,  has  caused  con- 
siderable loss,  particularly  in  warm  dry  seasons.  A  few  years 
ago  it  was  discovered  that  this  condition  was  caused  by  a 
very  small  whitish  leaf-hopper  that  sucks  the  sap  from  the 
leaves.  When  the  plants  are  badly  infested  the  beets  become 
stunted,  or  shrivel,  and  are  of  little  or  no  value. 

So  far  no  practicable  means  of  control  has  been  found,  but 
if  the  land  is  kept  moist  and  other  conditions  made  favorable 
for  the  plants  they  will  be  better  able  to  withstand  the  loss 


484    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

due  to  the  insects'  feeding.  Spraying  with  contact  insecti- 
cides has  been  suggested,  but  as  the  insects  feed  on  the  under- 
side of  the  leaves  it  is  difficult  to  reach  them. 

Web -worms. — There  are  three  or  more  species  of  web-worms 
(caterpillars)  that  attack,  and  sometimes  defoliate  beets  and 
other  garden  plants.  They  are  called  web-worms  on  account 
of  their  habit  of  spinning  fine  webs  as  they  feed.  The  invaded 
plants  may  be  killed  outright,  or  only  retarded  in  their  develop- 
ment. The  slender,  greenish  worms  are  marked  with  many 
small  black  spots  and  sometimes  with  lighter  markings.  When 
fully  developed  they  enter  the  ground  and  spin  long  slender 
cocoons  in  which  they  pupate.  The  adult  moths  are  greenish 
or  brownish  and  have  a  wing  expanse  of  about  an  inch. 

They  may  be  controlled  by  spraying  with  Paris  green  or 
arsenate  of  lead.  If  the  field  is  plowed  late  in  the  fall  many  of 
the  pupae  will  be  destroyed.  As  these  worms  feed  on  other 
plants,  including  many  of  the  common  weeds,  it  is  evident 
that  these  should  be  kept  out  of  the  garden  or  fields. 

The  Beet  Aphis  (Pemphigus  beta). — Sometimes  the  beets 
in  certain  parts  of  the  field  are  found  to  be  much  smaller  than 
the  average,  and  soft  and  spongy  rather  than  firm  as  they  should 
be.  If  such  beets  are  taken  from  the  ground  they  may  be 
found  to  be  covered  with  a  mold-like  substance  which  is  really 
the  flocculent  excretion  from  many  little  plant-lice  that  are 
feeding  there.  As  long  as  this  insect  fed  on  yarrow,  door-mat 
weed,  grasses,  and  other  wild  plants  as  it  used  to,  it  was,  of 
course,  of  no  economic  importance,  but  as  soon  as  beets  began 
to  be  cultivated  in  the  region  where  it  occurred  it  found  them 
more  to  its  liking,  and  now  in  some  regions  many  tons  of  beets 
are  destroyed  by  it  each  year. 

If  this  pest  becomes  abundant  in  a  field  it  should  be 
starved  out  by  refraining  from  planting  beets  or  other  root 
crops  there  for  two  or  three  years. 

OTHER  GARDEN  INSECTS 

Cut-worms  and  Army-worms. — Most  of  the  common  dull 
grayish  cut- worms  (caterpillars  of  certain  owlet-moths),  hide 


INSECTS  INJURIOUS  TO  GARDEN  TRUCK    485 

away  in  the  ground  or  rubbish  during  the  day  and  come  forth 
at  night  to  feed  on  any  available  vegetation.  As  they  have  a 
pernicious  habit  of  cutting  off  small  tender  plants  close  to  the 
surface  of  the  ground,  they  may  often  do  much  damage,  par- 
ticularly in  the  garden.  They  are  usually  held  in  check  by 


FIG.  229. — A  cut-worm,  species  undetermined.     (About  natural  size.) 

their  natural  enemies,  but  sometimes  they  seem  to  get  away 
from  control  and  occur  in  such  numbers  that  they  destroy 
nearly  every  green  thing  in  the  affected  regions.  At  such 
times  some  of  the  species  will  begin  to  migrate  in  great  armies 


FIG.  230. — Adult  of  army-worm,  Leucania  unipimcla.      (About  natural 

size.) 

in  search  of  food.  They  are  then  called  army-worms,  and 
their  control  becomes  a  matter  of  prime  importance  to  the 
man  whose  field,  orchard  or  garden  lies  in  their  path. 

The  methods  used  in  fighting  cut-worms  must  vary  according 
to  time,  place  and  local  conditions.     No  single  remedy  can  be 


486    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

given  that  will  prove  equally  successful  at  all  times  and  places. 
Remedies  that  are  very  effective  under  ordinary  conditions 
often  become  wholly  useless  during  a  bad  outbreak.  Clean 
cultivation  will  materially  lessen  the  number  of  larvae  that 
occur  in  a  garden  under  ordinary  circumstances.  When 
the  worms  are  abundant  and  marching,  ditching  is  often  re- 
sorted to,  usually  with  very  satisfactory  results.  Banding 
trees  with  tanglefoot  or  some  similar  substance  is  helpful  in 
case  the  cut-worms  are  of  the  climbing  sort.  A  very  few  in  a 
garden  may  destroy  many  valuable  plants,  so  it  is  often  worth 
while  to  search  for  them  in  the  ground  around  the  plants,  and 
destroy  them.  Poisoned  baits  may  often  be  used  with  success. 
When  they  suddenly  appear  in  great  numbers  in  a  field  but 
little  can  be  done  to  control  them. 

The  Corn  Ear- worm  (Heliothis  obsoleta). — This  larva  bores 
unsightly  irregular  channels  on  the  ears  of  corn,  doing  particular 
damage  to  sweet  corn.  It  is  also  a  serious  pest  of  cotton,  feed- 
ing in  and  destroying  the  bolls;  hence  it  is  also  known  as  the 
cotton  boll-worm.  Tomato  fruit-worms  and  tobacco  bud- 
worms  are  among  some  of  the  other  names  that  are  applied 
to  this  pest,  which  attacks  almost  all  kinds  of  garden  crops  and 
many  forage  plants.  The  greenish-yellow  adult  moths  appear 
early  in  the  spring  and  lay  their  eggs  on  corn  and  other  food 
plants.  The  larvae  feed  about  a  month,  and  then  enter  the 
ground  to  pupate.  There  may  be  from  two  to  five  or  six  broods 
during  the  summer,  the  greatest  number  occurring  in  the  south 
where  the  feeding  season  is  longer. 

In  the  garden  about  the  only  satisfactory  means  of  control 
is  hand  picking.  It  is  seldom  practicable  to  spray.  In  the 
cornfield  the  time  of  planting  should  be  so  regulated  that  the 
corn  will  not  be  in  silk  when  the  moths  are  flying  most  abun- 
dantly. All  infested  land  should  be  plowed  late  in  the  fall  or 
during  the  winter,  as  this  will  destroy  many  of  the  over-winter- 
ing pupae. 

The  Striped  Cucumber-beetle  (Diabrotica  vittata). — These 
small,  yellow,  black-striped  beetles  attack  many  of  the  vines 
in  the  garden  as  soon  as  they  are  above  the  ground,  and  as  they 
often  occur  in  great  numbers  they  may  destroy  most  of  the 


INSECTS  INJURIOUS  TO  GARDEN  TRUCK    487 

young  tender  plants.  The  eggs  are  laid  in  the  soil  about  the 
food  plant,  and  the  slender  white  larvae  feed  on  the  roots, 
sometimes  doing  considerable  damage  there.  As  the  adult 
hibernates  in  the  ground  or  in  rubbish  in  the  field,  all  of  the 
vines  should  be  destroyed  as  soon  as  the  crop  is  off.  The  most 
practicable  method  of  protecting  the  young  vines  is  to  cover 
them  with  a  screen  that  will  keep  the  beetles  away.  Early 
squash  or  beans  may  be  planted  as  trap-crops  so  that  the 
insects  will  be  attracted  to  these  while  the 
other  vines  are  getting  well  started.  Air- 
slaked  lime,  tobacco  dust  or  other  powders 
thoroughly  dusted  over  the  plants,  afford 
some  protection,  especially  if  some  untreated 
trap-crop  is  near-by. 

Squash -bug  (Anasa  tristis). — This  rather 
large,  flattened,  blackish  bug  is  often  found 
sucking  the  sap  from  the  leaves  of  various 
vegetables,  but  it  is  found  most  commonly 
on  squash  vines.  The  adults  hibernate  in 
the  garden  and  appear  early  in  the  summer. 
The  eggs  are  laid  on  the  underside  of  the 
leaves.  The  wingless  young  or  nymphs  also 
feed  on  the  leaves.  In  the  south  there  may 
be  two  or  even  three  generations  during  the  year.  The  in- 
sects may  be  gathered  and  destroyed,  and  the  egg  masses 
may  be  easily  crushed  on  the  leaves.  Shingles  or  boards  or 
leaves  placed  on  the  ground  near  the  plants  make  good 
hiding  places  for  the  adults,  and  if  such  traps  are  examined 
in  the  evening  and  early  morning  many  of  the  bugs  may  be 
found  and  killed. 

The  Squash-vine  Borer  (Melittia  satyriniformis) . — Often 
the  squash  vines  wilt  and  die  because  of  the  attacks  of  a  whitish, 
black-headed  larva  that  bores  into  them.  Other  vines  may  also 
suffer,  but  the  late  varieties  of  squash  seem  to  suffer  most. 
The  borers  may  attack  almost  any  part  of  the  vine,  but  do 
most  damage  when  they  are  working  in  the  base,  for  they  may 
then  destroy  the  whole  vine.  The  adult  is  one  of  the  clear- 
winged  moths  (family  Sesiidce},  looking  somewhat  like  the 


FIG.  231.— The 
cucumber  -  beetle, 
Dial)  r  otic  a  12- 
punctata.  (Three 
times  natural 
size.) 


488     ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

peach-tree  borer.  The  eggs  may  be  laid  on  any  part  of  the 
plant.  In  the  South  there  may  be  two  generations  each 
year.  As  the  borers  feed  in  the  vine  they  cannot  be  reached  by 
insecticides.  A  gummy  exudation  usually  discloses  the  posi- 
tion of  the  larvae,  and  it  is  sometimes  worth  while  to  slit  the  vine 
open  and  kill  the  pest.  The  vines  should  be  burned  as  soon 
as  the  crop  is  gathered.  Fall  and  winter  plowing  and  crop 
rotation  will  help  to  control  such  insects  as  these. 

The  Onion-maggot  (Pegomyia  ceparum). — The  roots  and 
bulbs  of  onions  are  sometimes  attacked  by  small  white  maggots 
that  in  appearance  resemble  the  cabbage-maggot.  The 
adults  of  the  two  species  are  closely  related  and  can  only  be 
distinguished  by  close  examination.  The  cultural  methods 
suggested  for  controlling  the  cabbage-maggot  are  effective  in 
dealing  with  this  insect  also. 

The  Tomato -worms  or  Tobacco-worms  which  are  often 
serious  pests  on  tomato  vines  are  described  on  page  499. 


CHAPTER  XXXVI 
INSECTS  AFFECTING  FIELD  AND  FORAGE  CROPS 

As  the  great  field  crops  of  the  United  States  are  its  chief  wealth, 
the  insect  pests  that  attack  grains,  cotton  and  grasses  are  the 
most  important  animal  enemies  of  our  material  welfare.  The 
annual  losses  from  insect  attacks  on  cereals  amount  to  three 
hundred  million  dollars,  on  hay  and  forage  crops  to  sixty-six 
million  dollars  and  to  cotton  eighty-five  million  dollars.  The 
annual  losses  to  wheat  and  corn  caused  by  the  attacks  of  but 
two  insects,  the  Hessian-fly  and  the  chinch-bug,  must  amount 
to  a  hundred  million  dollars.  Too  much  time  and  care, 
then,  cannot  be  given  to  the  study  of  the  nature  of  the  grain 
pests  and  to  devising  means  of  lessening  their  ravages.  Be- 
cause of  the  enormous  supply  of  food  furnished  them  by  our 
great  fields  of  growing  grain,  their  numbers  may  become, 
without  restraint,  almost  inconceivable.  In  fact,  in  the  case 
of  all  the  insect  pests  of  fruits  and  crops  it  is  our  own  fault,  as 
it  were,  that  has  led  them  to  become  as  dangerous  to  these  crops 
as  they  are.  We  have,  by  our  planting  of  great  numbers  of 
one  kind  of  plant  together,  furnished  the  insects  such  bountiful 
supplies  of  food  that  their  enormous  increase  in  numbers  is 
an  inevitable  result.  It  is  this  encouraged  increase  that  con- 
stitutes the  danger.  The  number  of  chinch-bug  individuals 
that  can  live  at  one  time  in  a  growing  cornfield  of  hundreds  of 
acres  is  simply  inconceivable.  But  as  the  increase  of  animals 
proceeds  by  geometrical  ratio  while  the  addition  of  new  acres 
of  food  supply  can  increase  only  by  arithmetical  ratio,  the 
insect  numbers  finally  become  more  than  the  food  supply  can 
maintain  without  too  much  injury,  and  then  the  great  losses 
begin. 

The  grain  pests  are  of  great  variety  of  kind  and  habit. 
Aphids,  and  beetle  and  moth  larvae  attack  the  roots.  Biting 

489 


490    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

beetles  and  sucking  bugs  attack  the  leaves  and  stems.  The 
minute  whitish  larvae  of  small  flies  lie  in  the  stems  or  leaf  axils 
and  drain  the  sap.  Weevils  ravage  the  stored  grain.  Cotton 
has  its  peculiar  pests,  one  of  which  alone,  the  notorious  cotton 
boll-weevil,  that  came  into  this  country  from  Mexico  only 
twenty  years  ago,  has  in  the  last  decade  caused  an  annual 
loss  of  not  less  than  twenty-five  million  dollars. 

Grasses  and  forage  plants  have  an  exceptionally  wide  range 
of  insect  enemies,  and  enemies  that  for  the  most  part  are  very 
difficult  to  fight  successfully  in  any  inexpensive  way.  Most 
of  their  combating  must  be  done  by  such  general  agricultural 
methods  as  crop  rotation,  or  very  deep  or  unusually  late  or 
early  plowing,  etc. 

The  few  grain,  cotton,  and  forage  crop  pests  described  in  the 
following  paragraphs  comprise  the  ones  of  chief  importance, 
but  there  are  many  others  to  be  taken  into  account.  Students 
should  refer  to  sources  of  more  inclusive  and  detailed  informa- 
tion concerning  these  pests.  The  bulletins  of  the  government 
and  state  bureaus  of  entomology  are  good  sources  for  this 
information.  Sanderson's  "  Insect  Pests  of  Farm,  Orchard  and 
Garden,"  already  mentioned,  is  a  good  recent  manual. 

CORN 

The  Western  Corn-root  Worm  (Diabrotica  longicornis) . — 
This  is  a  slender  larva,  or  grub,  that  bores  into  the  roots  of  young 
corn  and  seriously  interferes  with  its  development.  Sometimes 
these  larvae  will  destroy  the  greater  part  of  the  root  system  so 
that  the  plant  either  dies,  or  is  easily  blown  over  by  the  wind, 
or,  if  it  lives,  is  unproductive.  The  adult  is  a  small  bluish- 
green,  leaf-eating  beetle  about  one-third  of  an  inch  long.  The 
eggs  are  laid  in  the  ground  in  the  fall  near  the  roots  of  the  corn 
and  do  not  hatch  until  the  following  spring.  As  the  larvae  feed 
only  on  corn  it  is  evident  that  a  system  of  crop  rotation  will  con- 
trol the  pest. 

The  Southern  Corn-root  Worm  (Diabrotica  i2-punctata}. — 
The  larva  of  this  species  is  similar  in  appearance  and  habits  to 
the  one  just  described,  but  it  has  a  wider  range  of  food  plants. 


INSECTS  AFFECTING  FIELD  CROPS          491 

The  wing-covers  of  the  small  bright-green  beetle  are  marked 
with  twelve  black  spots.  The  beetle  feeds  on  the  foliage  of 
many  garden  and  field  plants,  often  doing  considerable  damage. 
On  account  of  this  wide  range  of  food  plants  it  is  not  as  easily 
controlled  as  the  preceding  species,  but  crop  rotation  will  still 
be  of  some  value.  Sometimes  it  is  profitable  to  plant  the  corn 
so  late  that  it  will  not  come  up  until  after  the  beetles  have  laid 
their  eggs  on  other  plants. 

The  Cora-root  Web -worm  (Cr ambus  caliginosellus). — This  is 
still  another  larva  that  attacks  the  roots  and  stalks  of  corn, 
sometimes  killing  so  many  of  the  young  plants  that  the  field 
must  be  reseeded.  The  yellowish  or  brownish  little  cater- 
pillars, covered  with  a  case  made  out  of  loose  web  and  particles 
of  dirt,  are  usually  found  feeding  in  the  corn  plant  below  the 
surface  or  close  to  the  surface  of  the  ground.  The  adults  are 
small,  white  and  yellowish  "grass-moths,"  so  called  because 
they  are  so  frequently  seen  flying  from  the  grass  when  it  is 
disturbed.  When  the  moths  are  at  rest  the  wings  are  folded 
close  around  the  body.  The  larvae  of  the  second  generation 
hibernate  in  their  silken  tubes,  and  are  ready  to  begin  feeding 
as  soon  as  the  plants  begin  to  grow.  As  the  larvae  live  on  the 
roots  of  grasses,  corn  that  is  planted  on  new  land  will  suffer 
most.  In  well-cultivated  fields  where  crop  rotation  and  late 
fall  or  early  spring  plowing  is  the  practice  the  injury  is  usually 
not  so  great. 

The  Larger  Corn-stalk  Borer  (Diatrce  zeacolella). — This  in- 
sect belongs  to  the  same  family  of  moths  as  the  preceding  species 
but  it  is  larger.  The  larvae  live  in  the  stalk  of  the  corn,  often 
weakening  it  so  that  it  is  easily  broken  by  the  wind.  In  the 
fall  the  caterpillars  of  the  second  generation  bore  deep  into  the 
tap-root  and  there  pass  the  winter,  pupating  early  in  the 
spring.  If  the  old  stalks  and  butts  are  dragged  together  and 
burned  most  of  these  over-wintering  larvae  will  be  killed. 
Again,  crop  rotation  is  recommended  as  the  best  remedy. 

The  Bill-bugs  (Sphenophorus  spp.). — There  are  several 
species  of  snout  beetles,  or  weevils,  that  injure  corn  and  other 
field  crops  by  attacking  the  stalk  and  roots.  They  are  usually 
injurious  in  both  the  larval  and  adult  stages,  and  are  hard  to 


492    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

control.  One  species,  at  least,  passes  the  winter  in  the  corn 
stubble,  and  can  be  killed  by  burning  the  stubble.  They  will 
all  be  less  injurious  in  fields  where  root  crops  are  rotated  with 
corn  or  wheat  crops. 

The  Corn-root  Aphis  (Aphis  maidi-rddicis). — Sometimes  the 
corn  roots  are  badly  infested  with  little  greenish  plant-lice 
that  suck  the  sap  from  the  plant.  The  life-history  of  this 
insect  is  especially  interesting  as  it  shows  the  close  relation  that 
ants  and  plant-lice  sometimes  bear  to  each  other.  In  the  fall 
the  little  brown  field  ants,  Lasius  brunneus,  gather  the  eggs 
that  have  been  laid  by  the  aphids  in  the  ground,  and  store  them 
in  their  nests.  Here  they  are  cared  for  until  they  begin  to  hatch 
in  the  following  spring.  The  ants  then  carry  the  young  plant- 
lice  to  the  roots  of  grasses  or  weeds  that  grow  in  the  cornfield 
and  carefully  tend  them  there,  moving  them  to  new  plants 
when  the  old  ones  become  overcrowded.  When  the  corn  is 
planted  many  of  the  aphids  are  transferred  to  the  roots  of  the 
corn,  and,  as  they  increase  in  numbers  very  rapidly,  much 
damage  may  be  done  in  some  fields.  Because  the  ants  tend 
them  with  such  care  and  receive  in  return  the  honey-dew 
that  is  secreted  by  them  these  aphids  are  often  called  "ant- 
cows." 

If  grasses  or  weeds  are  not  allowed  to  grow  in  the  field  during 
the  early  spring  most  of  the  aphids  will  starve  before  the  corn 
sprouts. 

The  Corn  Ear-worm,  which  frequently  does  much  damage 
in  the  field;  has  been  discussed  on  page  486. 

WHEAT 

Chinch-bugs  (Blissus  leucopterus). — The  adult  chinch-bugs 
are  only  about  one-fifth  of  an  inch  long.  The  body  is  dark- 
colored,  and  the  whitish  wings,  which  lie  folded  over  the  back, 
are  each  marked  by  a  dark  triangular  spot.  The  very  young, 
often  called  "red-bugs,"  have  no  wings,  but  these  gradually 
develop  as  the  insect  passes  through  its  successive  molts. 
Because  of  their  habit  of  assembling  in  such  great  numbers  on 
the  stems  of  wheat,  corn  and  many  other  field  crops,  the 
chinch-bugs  are  often  the  worst  pest  the  farmer  has  to 


INSECTS  AFFECTING  FIELD  CROPS          493 

contend  with.  The  insects  hibernate  in  old  corn  stalks,  dead 
leaves,  clumps  of  grass  or  other  sheltered  places  in  the  field  or 
roadside.  As  soon  as  the  grasses  or  grains  begin  to  grow  they 
begin  feeding  on  them  and  lay  their  eggs,  from  which  the  first 
brood  of  young  soon  issues.  They  may  do  serious  injury  to 
the  wheat  or  other  small  grains  before  the  crops  ripen.  About 
the  time  the  wheat  is  ready  for  harvest 
the  chinch-bugs  migrate  to  oats  or  young 
corn.  Fortunately,  they  do  not  fly  when 
making  these  migrations,  but  crawl  slowly 
from  field  to  field.  The  eggs  from  which 
the  second  brood  are  to  hatch  are  laid  in 
the  corn.  The  young  of  this  brood  be- 
come mature  late  in  the  fall  and  seek 
out  suitable  places  to  hibernate.  If  corn 
is  not  available  the  whole  season  may  be 
passed  on  grasses. 

Many  years  ago  it  was  discovered  that 
the  chinch-bugs  were  attacked  by  a 
fungus  disease  that  sometimes  very  effec- 
tively controlled  them.  When  infected 
bugs  are  taken  into  the  laboratory  and  times  natural  size.) 
placed  in  boxes  with  healthy  bugs,  the 
latter  soon  become  infected.  These  infected  bugs  may  then 
be  sent  into  the  fields  and  placed  on  badly  infested  plants. 
In  this  way  the  disease  rapidly  spreads,  and  when  the  climatic 
conditions  are  right  it  soon  destroys  most  of  the  chinch- 
bugs  in  the  field.  But  this  method  of  control  has  not  been 
wholly  satisfactory  because  in  cool  and  dry  weather  the  disease 
does  not  spread  fast  enough. 

Clean  culture  is  of  prime  importance.  If  the  adult  bugs 
that  are  hibernating  in  the  fields  or  in  grasses  by  the  roadside 
and  fences  are  destroyed  by  burning,  there  will  be  no  injury 
in  the  following  spring.  When  the  insects  are  migrating  from 
the  wheat  to  the  corn  they  may  be  effectively  checked  by 
barriers  of  dust  or  coal  tar.  The  dust  barrier  is  made  by 
plowing  and  thoroughly  pulverizing  a  narrow  strip  of  ground 


FIG.  232.  — The 


494    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

and  then  making  a  deep  furrow  in  it  across  which  the  chinch- 
bugs  cannot  pass.  The  furrow  must  be  kept  in  good  condition 
by  frequent  cleaning  or  dragging.  In  wet  weather  it  will  be 
necessary  to  resort  to  a  barrier  made  by  a  narrow  line  of  coal- 
tar  or  some  similar  substance  placed  across  the  path  of  the 
invaders.  Such  barriers  require  constant  care  and  attention 
during  the  ten  days  or  two  weeks  that  the  bugs  are  migrating. 
Sometimes  when  the  chinch  bugs  have  gained  an  entrance  into 
a  cornfield  those  that  have  massed  on  the  first  few  rows  of 
corn  can  be  destroyed  by  a  blast  torch  or  by  spraying  with 
kerosene  emulsion. 

The  Hessian-fly  (M ayetiola  destructor) . — Probably  about  10 
per  cent,  of  the  wheat  crop  is  destroyed  annually  by  the  Hessian- 
fly  and  in  some  regions  the  loss 
may  reach  40  or  50  per  cent,  in  bad 
years.  The  adult  is  a  very  small 
blackish  fly  with  a  pair  of  delicate 
wings  that  are  provided  with  very 
few  veins.  The  eggs  are  usually 
laid  on  the  leaves,  and  the  larvae 
make  their  way  toward  the  base  of 
the  stem  where,  protected  by  the 
leaf  sheath,  they  begin  sucking  the 

•   A«.  ,T   -s      a      iuice  from  the  plant.     The  pupar- 

FIG.  233. — The  Hessian-fly,   J          .         ,  .  »       , 

Mayetiola  destructor,  adult  mm  in  which  the  pupal  stage  is 
male.  (Much  enlarged;  after  passed  looks  so  like  a  flax  seed  that 

the  pupal  stage  is  usually  referred  to 

as  the  "  flax-seed  stage."  There  may  be  one  to  four  generations 
a  year,  according  to  the  region  and  climatic  conditions,  but  the 
early  spring  and  late  fall  broods  are  most  destructive.  The 
flies  that  issue  late  in  the  fall  lay  their  eggs  on  the  young  win- 
ter wheat,  and  the  pupal,  or  flax-seed,  stage  is  reached  before 
cold  weather  comes.  The  adults  issue  from  these  pupae  early 
the  next  spring. 

The  best  method  of  control  is  to  refrain  from  planting  the 
wheat  in  the  fall  until  the  flies  have  laid  their  eggs  elsewhere. 
Only  a  close  study  of  the  fly  and  the  weather  conditions  that 
control  its  time  of  issuing  in  the  fall  will  enable  one  to 


INSECTS  AFFECTING  FIELD  CROPS          495 

choose  the  right  date  for  sowing.  After  conducting  long  series 
of  experiments  the  United  States  Bureau  of  Entomology  has 
suggested  the  following  dates  as  safe  for  sowing  wheat  in  aver- 
age seasons:  in  northern  Michigan  soon  after  the  first  of  Sep- 
tember; in  southern  Michigan  and  northern  Ohio,  about 
September  20;  in  southern  Ohio,  after  the  first  week  in  October; 
in  Kentucky  and  Tennessee,  October  10  to  20;  in  Georgia  and 
South  Carolina,  October  20  to  November  15.  The  exact 
time  will  also  depend  upon  altitude  as  well  as  latitude.  Crop 
rotation,  thorough  cultivation,  clean  culture  and  the  use  of 
good  fertilizers  are  all  important  in  regions  where  the  Hessian- 
fly  is  a  bad  pest.  No  varieties  of  wheat  thus  far  found  are 
wholly  exempt  from  the  attacks  of  the  fly  but  some,  on  account 
of  their  habit  of  growth,  withstand  the  injury  better  than  others. 

The  larvae  of  certain  other  flies  may  also  often  be  found 
working  in  the  wheat  in  much  the  same  way  as  the  Hessian-fly, 
but  they  rarely  occur  in  sufficient  numbers  to  do  serious 
damage. 

The  Wheat  Joint -worm  (Isosoma  tritici}. — The  joint- worms 
occur  in  the  stems  of  the  wheat  causing  them  to  swell  slightly 
and  become  hard  and  woody  so  that  the  grain  is  not  well 
nourished.  The  adults  are  small  black  insects  belonging  to 
the  family  Chalcidida,  nearly  all  the  other  members  of  which 
are  parasitic.  Crop  rotation  is  the  best  means  of  control. 
Infected  straw  and  stubble  should  be  burned  before  the  adult 
insects,  which  are  overwintering  in  such  places,  issue. 

The  Wheat  Straw-worm  (Isosoma  grandi}. — This  insect  is 
closely  related  to  the  preceding  species,  but  has  somewhat 
different  habits.  Many  of  the  members  of  the  spring  brood 
are  wingless  and  look  much  like  small  ants.  The  eggs  are  laid 
on  the  young  wheat,  and  the  larvae  frequently  destroy  the  whole 
plant  by  eating  out  the  crown.  The  adults  of  the  next  genera- 
tion are  larger  and  provided  with  wings  so  that  they  may  fly 
considerable  distances.  The  young  that  hatch  from  the  eggs 
of  this  brood  work  in  much  the  same  way  as  the  wheat  joint- 
worms.  They  pass  the  winter  in  the  pupal  stage  in  the  straw. 

The  control  measures  are  the  same  as  for  the  wheat  joint- 
worm. 


4g6    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

The  Grain-aphis,  or  Green -bug  (Toxoptera  graminum)  — 
This  little  green  plant-louse  sometimes  seriously  injures  young 
wheat  plants  by  sucking  out  the  sap.  They  do  most  damage 
in  the  south,  where  the  open  winters  often  allow  them  to  feed 
and  reproduce  during  the  whole  year.  In  such  instances  they 
become  so  abundant  on  the  winter  wheat  that  whole  crops  may 
be  ruined  as  early  as  March  or  April.  As  long  as  the  tempera- 
ture is  above  56°  F.  the  green-bugs  are  held  in  check  by  a 
minute  wasp-like  parasite,  Lysiphlebus  testaceipes,  and  it  is 
only  during  the  winter  time,  when  it  is  warm  enough  for  the 
pest  to  breed  but  too  cold  for  the  parasite,  that  the  plant-lice 
become  destructively  abundant.  Oats  are  the  favorite  food 
of  these  aphids,  and  they  seldom  do  much  damage  in  places 
where  volunteer  oats  are  not  allowed  to  grow. 

When  small  injured  spots  appear  in  the  field  late  in  the  winter 
the  green-bugs  in  such  areas  should  be  killed  by  spraying  with 
kerosene  emulsion,  or  by  burning  straw  over  them,  or  by  plow- 
ing under  the  infected  grain. 

STORED  GRAIN 

Stored  grains  are  often  attacked  by  the  larvae  of  beetles  or 
moths,  and  unless  preventive  measures  are  adopted  much  of 
the  grain  may  be  destroyed. 

The  Grain-weevil  (Calandra  granaria) ,  and  the  Rice -weevil 
(C.  oryzce). — Weevils  are  usually  the  most  common  pests  of 
stored  grain.  They  are  small  beetles  with  long  snouts,  with 
which  they  puncture  the  grain,  thus  making  a  place  where  the 
egg  may  be  inserted.  The  larvae  are  short,  thick,  legless  grubs 
that  feed  in  the  grain  until  ready  to  pupate.  The  beetles,  too, 
feed  on  the  grain,  and  as  they  increase  in  numbers  very  rapidly 
a  slight  infestation  may  soon  assume  serious  proportions. 
Grain  should  be  stored  only  in  clean,  tight  bins.  If  this  pre- 
caution is  taken  but  little  loss  will  be  suffered  on  account  of 
these  pests.  If,  however,  the  grain  becomes  infested,  it  should 
be  treated  with  carbon  bisulphide,  using  about  five  pounds  for 
every  1000  cubic  feet,  or  even  more  if  the  room  is  not  tight. 
Best  results  will  be  obtained  if  the  temperature  is  70°  F.  or 
higher.  Dishes  containing  the  liquid,  or  cotton  or  waste 


INSECTS  AFFECTING  FIELD  CROPS          497 

saturated  with  it,  should  be  placed  on  top  of  the  grain.  As 
the  gas  that  comes  from  it  is  heavy  it  will  sink  and  reach  all 
parts  of  the  bin.  Remember  that  this  gas  is  inflammable  and 
explosive.  If  the  grain  in  the  bins  can  be  heated  to  120°  F.  all 
the  weevils  in  all  stages  of  development  will  be  killed. 

The  Saw-toothed  Grain-beetle  (Silvanus  surinamensis). — 
Unlike  the  weevils,  which  are  somewhat  cylindrical,  this  small 
grain-beetle  is  quite  flat.  It  may  easily  be  recognized  by  the 
serrate  margins  of  the  prothorax.  The  larvae  are  long  and 
slender  and  provided  with  six 
legs,  enabling  them  to  move 
about  freely  and  thus  injure 
several  grains.  The  methods 
of  control  are  the  same  as  for 
the  weevils. 

The  Angumois  Grain-moth 
(Sitotroga  cerealella) . — In  the 
south  the  grain-moth  is  even 
a  worse  pest  than  the  weevils 
for  it  often  occurs  in  almost 
incredible  numbers  and  attacks 
wheat  in  the  field  as  well  as  in 
the  granaries.  The  moths  fly 
from  the  storerooms  while  the 
wheat  is  heading,  and  lay  their  eggs  on  the  grain.  The  larvae 
make  their  way  into  the  kernels  and  become  full  grown  about 
the  time  the  wheat  is  mature.  Other  generations  follow, 
the  members  of  each  attacking  the  grain  wherever  it  is 
found,  in  the  field,  in  the  stack,  or  in  store-rooms.  Corn  is 
not  attacked  as  often  as  wheat,  but  seed  corn  stored  in  barns 
may  often  be  badly  injured.  The  grain  should  be  threshed 
as  early  as  possible  and  stored  in  tight  bins  or  good  sacks.  If 
it  becomes  infested  while  stored,  it  may  be  treated  with  car- 
bon bisulphide.  Cleanliness  about  the  barns  and  particularly 
around  the  granaries  is  most  essential.  Badly  infested  grain 
may  be  fed  to  chickens  or  hogs. 

The   Mediterranean   Flour-moth    (Ephestia  kuehniella)  .— 
Mills  are  sometimes  overrun  with  the  larvae  of  a  small  grayish 


FIG.  234. — Adult,  pupa,  and 
larva,  of  the  saw-toothed  grain- 
beetle,  Silvanus  surinamensis. 
(Much  enlarged;  after  Howard  and 
Marlatt.) 


moth.  The  larvae  spin  little  silken  tubes  which  protect  them 
while  they  are  feeding  in.  the  flour  or  waste  about  the  mill. 
When  full  grown  they  wander  about  in  search  of  a  suitable 
place  to  pupate,  spinning  a  web  wherever  they  go.  It  is  this 
habit  that  renders  them  most  injurious,  for  the  infested  flour 
and  many  parts  of  the  mill  become  filled  with  the  webs.  This 
necessitates  frequent  and  expensive  stoppings  of  work  in  the 
infested  mills.  Great  cleanliness  about  the  mill  is  necessary. 
When  the  insect  becomes  troublesome  the  mill  should  be 
closed  tightly  and  fumigated  with  hydrocyanic  acid  gas  under 
the  direction  of  some  experienced  person.  If  the  temperature 
throughout  the  mill  can  be  raised  to  about  120°  F.  and  main- 
tained there  for  a  day,  all  moths,  pupae,  larvae  and  eggs  will 
be  killed. 

COTTON 

The  Boll-weevil  (Anthonomus  grandis). — There  are  several 
important  enemies  of  the  cotton  plants,  but  during  the  last  few 
years  the  boll-weevil  has  become  so  important  as  to  over- 
shadow almost  all  the  others.  Indeed,  one  of  these  insects, 


FIG.  235. — Boll-weevil,  Anthonomus  grandis.     (Much  enlarged.) 

the  cotton-worm,  which  was  formerly  looked  upon  as  one  of 
the  worst  enemies,  is  now  regarded  with  some  favor  by  many 
planters  because  it  sometimes  aids  in  controlling  the  weevil  by 
stripping  the  late  foliage  from  the  plants  and  thus  depriving 
the  weevil  of  its  food. 

This  small,  brownish  snout  beetle  is  commonly  known  as  the 
Mexican  cotton  boll-weevil  because,  like  several  other  insect 
pests  of  the  south,  it  came  into  the  United  States  from  Mexico. 


INSECTS  AFFECTING  FIELD  CROPS          499 

The  beetles  attack  only  cotton.  Those  issuing  from  their 
winter  hiding  places  early,  feed  on  the  foliage  and  lay  their 
eggs  on  the  unopened  buds,  or  "squares,"  as  soon  as  they  com- 
mence to  form.  The  larvae  hatching  from  these  eggs  feed  for 
ten  or  twelve  days,  and  usually  cause  the  infested  squares  to 
fall  to  the  ground.  There  may  be  four  or  five  generations 
during  the  summer,  the  beetles  attacking  the  older  bolls  as 
soon  as  the  squares  are  no  longer  available.  The  adults  of  the 
last  generation  hibernate  in  old  cotton  plants  or  in  rubbish  in 
or  near  the  fields.  When  they  are  hunting  for  suitable  places 
in  which  to  hibernate  they  may  fly  for  considerable  distances, 
and  thus  the  distribution  of  the  species  is  provided  for. 

The  larvae  in  many  of  the  infested  squares  that  drop  to  the 
ground  will  perish  on  the  hot,  unshaded  soil.  It  is  therefore 
advisable  to  plant  the  rows  as  far  apart  as  practicable  and  to 
use  varieties  of  cotton  that  produce  little  foliage  in  order 
that  the  sun  may  shine  on  the  fallen  squares.  As  the  damage 
is  usually  worse  on  the  late  varieties  the  best  of  the  early 
varieties  should  be  selected  in  regions  where  there  is  danger  of 
boll- weevil  infestation.  Any  cultural  methods  that  will 
strengthen  the  plant  and  aid  in  the  early  maturing  of  the  bolls 
will  materially  increase  the  yield.  As  soon  as  the  crop  is 
gathered  all  the  cotton  stalks  and  all  the  rubbish  in  the  field 
*should  be  burned.  This  will  kill  many  of  the  insects,  and 
destroy  the  feeding  and  hibernating  places  of  most  of  those 
that  are  left. 

The  Cotton  Boll-worm,  which  is  the  same  as  the  corn  ear- 
worm,  has  been  discussed  on  page  486.  It  is  best  controlled 
in  the  cotton  field  by  plowing  late  in  the  fall,  thus  destroying 
the  over-wintering  pupae.  Early  varieties  of  cotton  should  be 
planted,  as  it  is  the  later  broods  of  moths  that  lay  their  eggs 
on  the  cotton,  the  corn  being  preferred  as  long  as  it  is  young  and 
available.  Late  planted  corn  in  or  near  the  cotton  fields  will 
sometimes  keep  the  boll-worm  away  from  the  cotton. 

TOBACCO 

Tobacco-worms,  or  Horn- worms.— The  large  greenish  horn- 
worms  (larvae  of  sphinx-  or  hawk-moths)  are  probably  the  most 


500    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

serious  pests  of  tobacco  in  the  United  States.  They  feed  on  the 
green  leaves,  and,  when  abundant,  may  cause  a  loss  of  from  10 
to  15  per  cent,  of  the  crop.  Two  species,  somewhat  similar 
in  appearance  and  habits,  are  found  throughout  the  tobacco 
growing  regions.  The  northern  tobacco-worm,  Phlegethontius 
quinqtiemaculata,  is  more  common  north  of  the  latitude  of 
Washington,  D.  C.,and  the  southern  tobacco-worm,  P.  sextata, 
is  the  species  usually  destructive  in  the  southern  tobacco 
fields . 


FIG.  236. — Tobacco-worm,  larva  of  the  hawk-moth,  Phlegethonlius  qitin- 
quemaculata,  feeding  on  tomato.     (About  1/2  natural  size.) 

The  adults,  which  are  large  grayish  sphinx-moths,  lay  their 
eggs  on  the  lower  surface  of  the  leaves.  The  larvae  feed  on  the 
leaves  and  become  full  grown  in  about  three  weeks.  They  are 
then  three  or  four  inches  long  and  dark  green  in  color  with 
white  stripes  on  the  sides.  On  the  northern  species  these 
white  markings  are  V-shaped,  while  on  the  southern  species 
they  are  simply  oblique  lines.  On  the  last  segment  of  the 
body  is  the  conspicuous  "horn,"  which  has  suggested  the  name 
"horn-worm."  The  larva?  burrow  into  the  ground  a  few 
inches  before  changing  to  the  brownish  pupae.  In  the  pupal 
stage  the  proboscis  of  the  forming  moth  is  inclosed  in  a  peculiar 
handle-like  sheath.  In  some  regions  these  pupae  are  known  as 


INSECTS  AFFECTING  FIELD  CROPS           501 

"horn-blowers."  During  the  summer  the  pupal  stage  lasts 
about  three  weeks,  and  there  may  be  two  or  even  three  genera- 
tions in  the  south. 

The  insect  passes  the  winter  in  the  pupal  stage.  Many  of 
the  pupae  can  be  destroyed  by  thorough  plowing  and  harrowing. 
As  the  larvae  are  usually  easily  detected  on  the  plant,  hand-pick- 
ing is  the  common  method  of  control  where  labor  is  cheap. 
Paris  green  dusted  or  sprayed  over  the  plants  has  long  been  a 
favorite  remedy,  but  as  this  sometimes  burns  the  foliage,  ar- 
senate  of  lead  is  now  more  commonly  used.  From  four  to  six 
pounds  of  arsenate  of  lead  to  100  gallons  of  water  are 
the  proportions  usually  recommended. 

These  same  horn-worms  are  often  important  enemies  of 
tomatoes. 

The  Tobacco  Flea-beetle  (Epitrix  parvula). — This  small, 
black  flea-beetle  looks  much  like  flea-beetles  more  commonly 
found  on  tomatoes,  potatoes  and  other  garden  plants.  Indeed, 
this  species  does, not  restrict  itself  to  tobacco,  but  may  often 
be  found  on  other  plants  in  the  field  and  garden.  The  beetles 
feed  on  the  foliage,  and,  when  abundant,  may  do  considerable 
damage,  particularly  to  young  plants.  The  slender,  whitish 
larvae  usually  feed  on  the  roots  of  weeds,  but  they  sometimes 
attack  the  roots  of  garden  plants  also.  They  pupate  in  the 
soil  when  fully  developed.  There  are  probably  several  genera- 
tions each  year. 

If  the  field  is  kept  free  from  weeds  there  will  be  less  oppor- 
tunity for  the  larvae  to  find  food.  Where  the  beetles  appear  in 
destructive  numbers  the  plants  should  be  sprayed  thoroughly 
with  arsenate  of  lead,  five  or  six  pounds  of  the  poison  to  100 
gallons  of  water.  The  tops  of  the  young  plants  may  be  dipped 
into  an  even  stronger  solution  of  the  poison  just  before  they 
are  set  out  if  there  is  danger  of  the  flea-beetles  attacking  them 
early. 

The  Tobacco  Leaf -miner  (Phthorimaa  operculella.} — This 
little  larva,  which  is  only  about  half  an  inch  long,  lives  between 
the  upper  and  lower  epidermis  of  the  leaves  causing  them  to 
split.  This  has  suggested  the  popular  name  of  "split-worm" 
for  the  pest.  Sometimes  the  larvae  come  to  the  surface  and 


502    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

wander  about  before  entering  the  leaf  in  another  place,  If  the 
leaves  are  well  sprayed  with  arsenate  of  lead  many  of  the 
larvae  will  be  poisoned  as  they  attempt  to  eat  their  way  into  the 
leaf  again.  The  adult  insect  is  a  small  grayish  moth  with 
minute  dark  spots  on  the  front  wings. 

The  Cigarette-beetle  (Lasioderma  serricorne). — This  minute 
brownish  beetle,  which  is  only  about  one-sixteenth  of  an  inch 
long,  and  its  whitish  grub  or  larva,  feed  on  dried  tobacco  when- 
ever they  can  find  it.  They  do  serious  damage  to  the  stored 
dried  leaves  and  to  cigars  and  cigarettes  after  they  have  been 
manufactured.  In  warm  factories  the  insect  may  breed 
throughout  the  year  and  increase  in  numbers  very  rapidly. 
As  this  pest  lives  and  breeds  in  any  kind  of  dried  tobacco  it  is 
necessary  to  keep  the  factory  clean  and  not  allow  fragments  or 
dust  to  collect  in  out  of  the  way  places.  Infested  tobacco  or 
tobacco  products  or  infested  factories  may  be  fumigated  with 
carbon  bisulphide  or  with  hydrocyanic  gas. 

There  are  several  other  insects  that  do  more  or  less  damage 
to  tobacco,  but  most  of  them  can  be  controlled  by  keeping  the 
field  and  its  immediate  vicinity  free  from  weeds,  especially 
those  weeds  that  are  nearly  related  to  the  tobacco  plant, 
or  by  spraying  with  arsenate  of  lead. 

GRASSES  AND  FORAGE  PLANTS 

The  Clover  Root-borer  (Hylastinus  obscurus) . — The  roots  of 
clover  are  often  attacked  by  a  short,  thick,  whitish  larva  that 
feeds  in  the  tap  root  or  the  larger  rootlets.  The  adult  insect  is 
a  beetle  only  about  one-eighth  of  an  inch  long  and  reddish- 
brown  in  color.  The  beetles  hibernate  in  the  infested  plants, 
and  early  in  the  spring  fly  to  new  plants  where  they  lay  their 
eggs.  Badly  infested  fields  should  be  plowed  up  as  soon  as  the 
crop  is  cut  so  that  the  roots  may  dry  out  and  the  larvae  starve 
before  they  are  ready  to  pupate.  This  insect  is  seldom  in- 
jurious in  pastures. 

The  Alfalfa  Weevil  (Phytonomus  murinus). — The  alfalfa 
weevil  has  recently  been  introduced  into  some  of  the  western 
states  and  threatens  to  become  a  serious  pest.  Both  the  larvae 


INSECTS  AFFECTING  FIELD  CROPS           503 

and  adults  feed  on  the  foliage  and  sometimes  on  the  stem  of  the 
plant  also,  so  they  are  capable  of  doing  much  injury.  The 
beetles  are  only  a  little  over  one-eighth  of  an  inch  long,  dark 
brown,  and  are  covered  with  short,  thick,  black  and  grayish 
hairs.  The  snout  is  short  and  curved. 

Among  the  control  measures  that  have  been  suggested  are 
cutting  the  first  growth  when  most  of  the  eggs  are  on  the 
plant,  disking  the  field  early  in  the  spring  and  dragging  the 
field  with  brush  after  the  crop  has  been  cut.  Every  effort  is 
being  made  to  prevent  the  spread  of  this  pest. 


FIG.  237. — Alfalfa  weevil,  Phytonomus  murinus.    (Much  enlarged.) 


Grubs. — Grass  and  pasture  lands  are  often  badly  infested 
with  large  white  grubs  which  feed  on  the  roots  of  the  plants 
growing  there.  These  may  remain  in  the  larval  stage  two  or 
three  years,  but  finally  transform  to  pupae  from  which  issue  the 
large,  brown  beetles  known  as  May -beetles,  or  June-bugs.  The ' 
beetles  fly  at  night  and  are  frequently  attracted  to  lights.  As 
these  same  insects  are  common  pests  of  corn  and  of  many  other 
cultivated  plants  it  is  not  well  to  let  them  become  numerous  in 
grass  lands  that  are  near  cultivated  fields.  Deep  plowing  late 
in  the  fall  will  destroy  or  expose  to  the  birds  many  of  the  larvae 
and  pupae.  Hogs  turned  into  an  infested  pasture  will  root 
out  and  eat  most  of  the  grubs. 

Wire-worms. — The  long,  cylindrical,  hard,  wire-worms  have 
habits  similar  to  the  grubs  just  discussed.  They  may  remain 
in  the  larval  stage  from  three  to  five  years  and  often  do  con- 
siderable damage  to  corn,  wheat,  potatoes  and  other  field  and 
garden  crops.  The  adults  are  the  well-known  click-beetles,  or 
snapping-beetles.  Late  fall  or  eary  spring  plowing,  and  crop 
rotation,  are  the  control  measures  usually  adopted. 


504    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

Grasshoppers. — There  are  many  species  of  grasshoppers  that 
occur  in  fields  or  meadows  in  greater  or  less  numbers  every 
year.  The  Rocky  Mountain  locust,  that  lives  permanently  on 
the  high  plains  of  some  of  the  Rocky  Mountain  states,  was  for 
many  years  the  best  known  of  these  because  of  its  great 
migrations  into  the  Mississippi  Valley  where  it  destroyed  all 
the  vegetation  to  be  found  there.  The  last  of  these  migrations 
was  in  1877.  The  settling  and  consequent  changed  conditions 
of  the  regions  in  which  this  grasshopper  breeds  have  put  a 
stop  to  the  great  flights. 

Grasshoppers  lay  their  eggs  in  masses  in  the  ground,  and  cover 
them  over  with  a  sticky  fluid  that  forms  a  capsule-like  covering 
when  dry.  Meadows  and  pastures  or  bare,  dry,  rather  firm 
ground,  are  the  places  usually  selected  for  egg-laying.  The  wing- 
less young,  or  nymphs,  that  issue  the  following  spring  feed  on 
grasses  or  any  other  available  vegetation.  When  the  food 
becomes  scarce  they  may  travel  in  great  numbers  as  do  the  army 
worms,  devouring  every  green  thing  in  their  path.  However, 
they  cannot  travel  far  in  this  wingless  stage,  and  even  after 
acquiring  their  wings  most  kinds  seldom  fly  far  from  their 
breeding  grounds,  and  so  are  easily  controlled.  If  the  places 
where  the  eggs  are  deposited  are  plowed  during  the  fall  or  early 
spring  most  of  the  eggs  will  be  destroyed  or  buried  so  deep  that 
the  young  cannot  come  to  the  surface  when  they  hatch.  It  is 
sometimes  practicable  to  burn  over  a  field  where  the  young 
occur  in  great  numbers  and  thus  destroy  them  before  they 
migrate  to  cultivated  fields.  On  hard  smooth  ground  many 
may  be  killed  by  rolling  with  a  heavy  roller.  When  the  nymphs 
are  migrating  a  field  may  be  protected  by  ditching  as  for  the 
army  worms  (page  484).  The  poisoned  mash  (page  415)  rec- 
ommended for  use  against  cutworms,  may  also  be  used  with 
success  against  the  grasshoppers.  Various  forms  of  hopper- 
dozers  have  been  contrived  for  catching  the  wingless  grass- 
hoppers. The  most  common  is  a  long,  shallow  pan  or  tray 
mounted  on  runners  in  which  is  placed  a  little  water  covered 
with  kerosene  or  crude  oil.  Oil  or  coal  tar  may  be  used 
without  the  water.  The  back  and  ends  are  provided  with 
walls  about  three  feet  high  to  prevent  the  grasshoppers  from 


INSECTS  AFFECTING  FIELD  CROPS           505 

jumping  over  it  when  the  apparatus  is  pulled  or  pushed  across 
the  field. 

Ordinarily  the  grasshoppers  are  pretty  well  controlled  by 
their  natural  enemies,  among  the  more  important  of  which  are 
birds,  the  larvae  of  blister-beetles,  tachina-flies  and  bee-flies, 
and  a  little  red  mite  that  attacks  the  nymphs  and  the  eggs. 


CHAPTER  XXXVII 
INSECTS  INJURIOUS  TO  FOREST  AND  SHADE  TREES 

Since  the  attention  of  the  American  people  has  been  called 
to  the  need  of  preserving  and  caring  for  the  forests  of  our  land, 
and  the  government  has  established  forest  reservations  in  all 
those  states  still  containing  extensive  wooded  areas,  the  study 
of  the  insect  pests  of  forest  trees  has  made  considerable  prog- 
ress. Although  in  European  countries,  especially  Germany, 
the  study  of  forest  insects  has  been  the  most  notable  part  of 
the  economic  entomological  work,  it  has  not  been  so  in  America. 
But  forest  preservation  is  a  much  older  science  in  Europe  than 
with  us,  where,  indeed,  it  is  a  very  recent  thing. 

The  insect  enemies  of  forest  trees  are  many,  and  often  very 
serious  in  their  ravages.  Especially  in  the  great  pine  forests 
are  the  insects  a  constant  menace,  and  too  often  a  menace 
realized.  Fire  is  the  only  other  forest  enemy  as  dangerous  as 
the  insects.  And  the  danger  of  fire,  because  less  insidious  and 
difficult  to  appreciate,  is  being  much  more  rapidly  lessened  by 
vigilant  care  and  effective  methods  of  prevention  than  is  the 
less  obvious  but  more  widespread  and  continuous  danger 
from  insect  attack. 

Forest  entomologists  estimate  the  annual  forest  loss  from 
insect  pests  at  one  hundred  million  dollars.  Yet  the  injuries 
to  shade  and  ornamental  trees  are  likely  to  have,  in  the  eyes  of 
most  of  us,  an  importance  that  outweighs  that  of  the  forest 
losses.  No  money  value  can  satisfactorily  be  assigned  to  a  row 
of  stately  elms  along  a  street  in  town  or  village,  nor  to  a 
single  well-placed,  splendid  old  oak  in  a  dooryard.  We  shall 
give,  therefore,  special  attention  in  this  brief  chapter  to  the 
insect  enemies  of  shade  trees  and  to  the  means  of  fighting  them. 
This  is  the  more  fitting,  also,  as  forest  insects  must  be  controlled 
rather  by  general  forestry  methods  and  the  work  of  specially 

506 


INSECTS  INJURIOUS  TO  FOREST  TREES      507 

trained  forest  rangers  and  caretakers  than  by  the  usual 
methods  of  the  economic  entomologist. 

The  few  insects  described  in  the  following  paragraphs  are 
perhaps  the  most  important  of  the  commoner  pests  of  shade 
trees,  but  there  are  many  others  of  similar  habits  which  may  be 
found  by  keen-eyed  and  persevering  students.  The  remedies 
for  these  others  will  be  of  the  same  general  nature  as  those 
recommended  for  the  insects  described,  although  modifications 
of  them  may  need  to  be  made  to  fit  particular  cases. 

Government  and  state  bulletins  will  give  further  and  more 
detailed  information  about  the  pests  briefly  described  here  and 
also  about  others  likely  to  be  found  on  the  trees. 

The  Gipsy-moth  (Porthetriadispar). — One  of  the  very  worst 
of  the  many  shade  tree  and  woodland  pests  is  the  gipsy-moth, 


FIG.  238. — Gipsy-moth,    Porthetria  dispar,  adult  female.     (About    1/4 
larger  than  natural  size.) 

which  was  introduced  into  this  country  from  Europe  about 
1868.  Fortunately  it  spreads  slowly  and  as  yet  occurs  only  in 
the  New  England  states.  The  federal  government  and  the 
states  concerned  are  now  spending  more  than  a  million  dollars 
a  year  in  trying  to  control  this  pest.  But  in  spite  of  all  their 
efforts  the  insect  is  gradually  widening  the  boundaries  of  the 
infested  areas,  and  other  localities  may  in  time  suffer  from  its 

ravages. 

The  brownish-yellow,  slender-bodied,  male  moth  flies  readily, 
but  fortunately  the  large,  sluggish  female  cannot  fly,  although 


508    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

she  is  provided  with  well  developed  wings.  The  female  has  the 
wings  whitish,  marked  with  small  black  spots  and  wavy  lines. 
She  lays  her  eggs  on  the  trees,  near-by  fences  or  hedges  or  other 
convenient  objects.  The  egg  masses,  which  consist  of  400  or  500 
eggs  covered  over  with  yellowish  hairs  from  the  insect's  body, 
remain  over  winter  in  these  places.  The  young  caterpillars, 
which  issue  early  in  May,  at  once  begin  feeding  on  any  available 
foliage.  They  are  covered  with  long  hairs,  and  as  they  swing 
from  the  branches  by  fine  silken  threads  they  may  be  carried 
by  winds  for  considerable  distances,  or  they  may  drop  on 
passing  vehicles  and  be  transported  for  some  miles  before  they 
drop  off.  Thus  new  localities,  not  too  far  away,  are  easily 


FIG.  239.— Gipsy-moth,  Porthetria  dispar,  larva.     (About  1/4  larger  than 

natural  size.) 

infected.  The  full-grown  dark-brown  larvas  attain  a  length  of 
about  three  inches,  and  attack  practically  all  kinds  of  wild  and 
cultivated  trees  and  shrubs.  A  deciduous  tree  will  often  live 
even  after  three  or  four  defoliations,  but  the  coniferous  trees 
die  after  one  complete  stripping. 

In  the  orchard  this  pest  may  be  fairly  well  controlled  by 
painting  the  egg  masses  with  creosote  sometime  during  the 
winter,  or  by  spraying  the  leaves  with  arsenate  of  lead  as  soon 
as  the  larvae  appear  in  the  spring.  In  the  woodlot  control  is 
much  more  difficult,  and  usually  even  impossible,  although  the 
same  measures  as  recommended  for  the  orchard  may  some- 
times be  practicable.  As  the  very  young  larvae  do  not  feed  on 
conifers  these  trees  may  be  protected  by  clearing  out  all  brush 
and  deciduous  trees.  In  its  native  home  this  insect  is  not  such 
a  serious  pest  because  it  is  controlled  by  its  natural  enemies. 


INSECTS  INJURIOUS  TO  FOREST  TREES      509 

For  several  years  the  U.  S.  Bureau  of  Entomology  has  been 
introducing  many  of  these  parasitic  and  predaceous  insects, 
hoping  that  some  would  prove  to  be  efficient  here.  A  measure 
of  success  has  attended  these  efforts  and  it  is  quite  possible  that 


FIG.  240. — Brown-tail  moth,  Euproctis  chrysorrhoza,  adult.     (About  1/4 
larger  than  natural  size.) 

when  enough  of  these  natural  enemies  have  been  established  in 
this  country  the  pest  may  be  overcome,  and,  in  the  future, 
kept  in  reasonable  control. 

The  Brown-tail  Moth  (Euproctis  chrysorrhaa) . — Like  the 
gipsy-moth  the  brown-tail  was  introduced  from   Europe,  but 


FIG.  241. — Brown-tail  moth,  Euproctis  chrysorrhaa,  larva.     (About  1/4 
larger  than  natural  size.) 

much  more  recently.  It  attacks  orchard  trees  and  almost 
all  kinds  of  shade  trees  except  the  evergreens.  The  moths  are 
snow-white,  with  a  conspicuous  brown  tuft  at  the  end  of  the 
abdomen.  They  fly  by  night,  and  are  attracted  by  lights,  so 
that  shade  trees  and  fruit  trees  in  towns  are  usually  first  to 


510    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

suffer  from  their  attacks.  The  insects  pass  the  winter  as  small 
larvae  that  hibernate  in  a  nest  made  of  leaves  and  tips  of  twigs 
fastened  together  with  silken  webs.  Some  of  the  hairs  of  the 
full-grown  larvae  cause  severe  irritation  when  they  touch  the 
human  skin.  This  is  regarded  by  many  as  the  most  serious 
phase  of  an  outbreak  of  this  pest.  As  yet  the  insect  occurs 


FIG.  242. — Tent  of  tent-caterpillar  on  a  live-oak  tree.     (Reduced.) 


only  in  some  of  the  New  England  states,  but  it  is  constantly 
being  introduced  into  other  states  on  nursery  stock,  and  unless 
great  care  is  taken  it  may  soon  become  established  elsewhere. 
The  winter  nests  containing  the  young  larvae  are  conspicuous 
on  the  leafless  trees,  and  should  be  pruned  off  and  burned.  Ar- 
senate  of  lead,  4  pounds  to  50  gallons  of  water,  will  kill  most  of 


INSECTS  INJURIOUS  TO  FOREST  TREES      511 

the  young  larva;  before  they  make  their  nests  if  the  trees  are 
sprayed  as  soon  as  the  eggs  are  hatched  in  the  late  fall. 

Tent -caterpillars  and  tussock-moths,  which  have  been  de- 
scribed in  the  chapter  on  orchard  insects,  and  many  other 
leaf-feeding  larvae,  often  do  much  damage  to  shade  trees.  A 
study  of  their  habits  and  life  history  will  usually  reveal  some 
vulnerable  point  and  suggest  the  control  measures  to  be 
adopted.  Where  arsenate  of  lead  is  used  it  is  usually  necessary 
to  use  4  or  5  pounds  to  50  gallons  of  water. 

The  Elm  Leaf -beetle  (Galerucella  luteola). — Elm  trees  are 
attacked  and  seriously  injured  by  many  different  insects.  In 
many  places  the  leaf-beetles  are  the  most  important  of  these 
pests.  These  beetles  are  about  one-fourth  of  an  inch  long  and 
greenish  or  yellowish  marked  with  darker  spots  and  lines. 
They  hibernate  in  protected  places  during  the  winter  and  feed 
for  awhile  on  the  young  leaves  in  the  spring  before  they  lay 
their  eggs.  The  larvae  feed  for  two  or  three  weeks  before  de- 
scending to  the  ground  to  pupate.  There  may  be  two  genera- 
tions each  year. 

Although  it  is  difficult  to  spray  trees  as  tall  as  elms  often 
grow  to  be,  without  the  use  of  special  apparatus,  yet  it  is  pos- 
sible to  construct  a  spraying  outfit  that  will  enable  the  operator 
to  reach  easily  all  parts  of  the  tree.  Infested  trees  should  be 
sprayed  with  arsenate  of  lead  as  soon  as  the  beetles  begin  to 
feed  in  the  spring,  and  again  about  two  weeks  later  when  the 
first  larvae  hatch.  Sometimes  later  sprayings  may  also  be 
necessary. 

Plant -lice  and  Scale -insects. — Many  of  the  plant-lice  that 
feed  on  the  foliage  of  various  shade  trees,  and  the  scale-insects 
that  may  attack  any  parts  of  the  trees  above  the  ground,  can 
often  be  controlled  by  spraying  with  kerosene  emulsion  during 
the  summer  or,  and  usually  better,  with  the  sulphur-lime  wash 
during  the  winter. 

The  Locust-borer  (Cyllene  robinia). — Locust  trees  are  often 
attacked  by  borers  which  after  a  little  while  penetrate  so  far 
into  the  wood  that  they  cannot  be  removed  or  killed.  These 
borers  are  the  larvae  of  dark-brownish  beetles  which  are  about 
an  inch  and  a  half  long  and  have  eight  or  ten  narrow  golden 


512    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

yellow  stripes  across  the  thorax  and  wing  covers.  Repeated 
attacks  may  kill  the  trees,  and  it  is  the  safest  policy  to  cut  out 
and  burn  all  infested  trees  in  order  that  they  may  not  serve  as 
breeding  places  for  new  generations  that  will  later  attack  sound 
trees. 

The  Carpenter -worm  (Prionoxystus  robinice). — The  larvae  of 
a  large,  grayish,  night-flying  moth  have  come  to  be  known  as 
"carpenter  worms"  because  they  work  so  readily  in  the  wood 


FIG.  243. — Elm  leaves  curled  by  elm  aphis,  Schizoneura  ulmi.     (Reduced.) 


of  many  of  our  shade  trees.  For  some  months  after  hatching 
the  larvae  burrow  in  the  sapwood,  and  when  several  of  them  are 
at  work  in  one  tree  they  may  kill  it  by  girdling.  As  they 
grow  older  the  larvae  bore  into  the  solid  wood,  making  large 
burrows  in  which  they  live  for  a  year  or  two  longer  before 
they  change  to  pupae.  As  these  borers  are  more  apt  to  be 
found  in  trees  that  have  the  bark  rough  or  scarred  or  wounded, 
care  should  be  taken  to  keep  the  bark  uninjured.  The  larvae 


INSECTS  INJURIOUS  TO  FOREST  TREES       513 

in  the  burrows  may  be  killed  by  injecting  a  little  carbon 
bisulphide  into  the  hole  after  the  castings  and  exudations  have 
been  cleared  from  the  entrance.  The  hole  in  the  bark  should 
then  be  filled  with  cement. 

The  Leopard-moth  (Zeuzera  pyrina)  .—The  leopard-moths  are 
beautiful  white  moths  that  have  their  bodies  and  wings  marked 
with  many  black  spots.  The  larvse  may 

be  found  in  any  part  of  the  tree,  but  they 

more  often  attack  the  smaller  limbs.     As 

they    work  principally    in   the  sapwood, 

the  affected  limbs  are  usually  killed.     The 

only  satisfactory  method  of  treatment  is 

to  cut  out  all  the  infested  wood  and  burn 

it.     It  is  easier  and  safer  to  sacrifice  the 

whole  tree  if  it  is  badly  infested.     The 

female  moths  do  not  fly  readily,  so  the 

infestation  does  not  spread  rapidly  except 

in  places  where  the  trees  are  very  close 

together. 
The  Oak-primer  (Elaphidion  mllosum). 

—When  oak-pruner  beetles  occur  in  con- 
siderable numbers  the  trees  are  made  un- 
sightly by  the  dead  branches  which  later 

fall  to  the  ground.     The  damage  is  done 

by  the  larvse,  which  bore  in  the  twigs  and 

finally  cut  them  off.     As  the  larvae  pupate 

in  the  fallen  twigs  they  should  be  gathered 

and  burned  before  the  adult  beetles  issue. 

This  insect  attacks  many  kinds  of  shade 

trees,  and  sometimes  may  be  injurious  to       v  w    , 

.       ,      .  ,  rlG.      244.      WOrK 

certain  fruit  trees  also.  of   oak  twig-girdler, 

On  the  Pacific  Coast  there  is  another  AgrUus  sp.  (About 
smaller  borer,  Agrilus  politus,  that  attacks  2/3  natt 
and  kills  the  small  branches  of  the  oak  trees.  As  the  twigs 
are  killed,  but  not  cut  off,  the  tree  soon  becomes  very  ragged 
and  unpleasing  in  appearance.  Such  infested  twigs  should  be 
cut  off  some  time  during  the  winter. 


33 


5H    ECONOMIC  ZOOLOGY  AND  ENTOMOLOGY 

FOREST  INSECTS 

A  certain  amount  of  insect  injury  is  occurring  in  almost  every 
great  forest  all  the  time,  while  from  time  to  time  particular 
forests  are  devastated  by  the  outbreaks  of  certain  insects  that 
kill  practically  all  of  the  trees  in  the  affected  regions.  In  some 
instances  these  outbreaks  have  spread  over  50,000  square  miles, 


FIG.  245. — Work  of  a  bark-borer,  Phlceosinus  cristatus,    on    Monterey 
cypress.    (Reduced.) 

and  trees  that  would  have  produced  millions  of  feet  of  lumber 
have  been  destroyed.  Each  year  there  are  lesser  outbreaks 
when,  although  comparatively  few  trees  may  be  killed,  many  are 
retarded  in  their  growth  or  so  distorted  or  injured  that  they 
make  only  second-  or  third-class  lumber.  Altogether  the 


INSECTS  INJURIOUS  TO  FOREST  TREES      515 

annual  loss  to  our  forests  from  insect  attacks  must  amount  to 
many  millions  of  dollars. 

A  great  part  of  this  injury  is  due  to  the  work  of  the  bark- 
beetles,  belonging  to  the  family  Ipidce.  These  are  small, 
robust,  blunt-headed  beetles  which  burrow  into  the  bark  to 
lay  their  eggs,  and  whose  larvae  burrow  out  through  the  live 
bark  in  all  directions  from  the  egg  chambers.  Of  these  bark- 
beetles  the  members  of  the  genus  Dendroctonus  are  the  largest 
and  the  most  important.  The  adult  beetles  bore  into  the  bark 
until  they  reach  the  cambium  where  each  species  makes  a 
characteristic  kind  of  burrow.  The  larvae  also  make  character- 
istic chambers  in  the  bark  or  on  the  surface  of  the  wood  so.that 
one  who  is  acquainted  with  their  work  can  always  tell  from  the 
nature  of  the  borings  just  which  species  has  been  at  work  on  a 
tree.  The  members  of  the  genera  Ips,  Scolytus,  and  others  also 
frequently  do  considerable  damage.  For  a  long  while  it  was 
believed  that  nothing  could  be  done  to  control  the  spread  of 
these  insects  in  the  forests.  But  a  study  of  their  life- history 
suggested  that  many  of  them  might  be  controlled  by  cutting 
out  the  infested  trees  and  thus  destroying  the  immature 
stages  of  the  beetles  before  the  adults  issue  to  attack  new  trees. 
Experience  has  shown  that  this  is  practicable,  and  the  Bureau 
of  Entomology  has  agents  in  the  principal  forest  regions  to 
direct  properly  the  work  of  cutting  wherever  the  owners  care 
to  undertake  it. 


Abalone,  232 
Acanthia  lectularia,  395,  *3g6 
Acanthocephala,  87 
Acarina,  209 
Achroia  grisella,  196 
Acipenserida;,  247 
Acropora  muricata,  *67 
Actinozoa,  67 
Adaptation,  346 
Adelochorda,  237 
Adoxus  viiis,  466 
Aegcria  tipuliformis,  *^6g 
African  tick  fever,  356 
Agelina  sp.,  *2og 
Agkistrodon  cantor trix,  270 

A.  piscivoris,  270 
Agrilus  sp.  injury,  *5i3 

A.  politus,  513 

A.  ruficollis,  468 
Alee  americana,  303 
Aleurodes  citri,  451 

A.  nubifera,  452 

A.  howardi,  452 
Alfalfa  weevil,  502,  *$O3 
Alligator  mississippiensis,  264 
Alligators,  264 

Alternation  of  generations,  65 
Alosa,  249 

Alsophila  pometaria,  429 
Amblyomma  variegatnm,  *2ii 
Amblystoma  tigrinum,  '257 
Ammophila,  *i83 
Amoeba,  structure  and  habits, 

*26 
Amceba  dysentercz,  350,  *35i 

A.  mcleagridis,  351 
Amcebic  dysentery,  350 
Amphibia,  239,  256,  257 
Amphineura,  222 
Amphipoda,  121 
Anarsia  lineatella,  435 


INDEX 

(Numbers  marked  with  *  indicate  illustrations.) 


Anasa  tristis,  487 
Anas  boschas,  332 

A.  cinereus,  332 

A.  cygmoides,  332 
Anchovies,  250 
Anguillidas,  249 
Anguillula  sp.  *jg 
Animals,  branches  and  classes,  54 

classification,  48,  55 

domesticated,  321,  7 

denned,  i 

names,  50 

Ankylostomiasis,  84 
Annelida,  98 
Anolis  principally,  265 
Anopheles,  larvae,  *37i 

A.  maculipennis,  *36o,  *372 

wing,  *372 
Anosia  plexippus,  metamorphosis, 

"151 

Anseres,  280 
Ant-eater,  300,  301 
Antelope,  303 

Antennae,  different  kinds,  *i3o 
Anthonomus  grandis,  *4g8 

A.  signatus,  473 
Anthrenus  scrophiilaritz,  *4oi 
Antilocapra  americana,  303 
Ant-lion,  167 
Ants,  199,  398 

Argentine,  398,  *399 

black,  399 
25,  nest,  artificial,  *2os 

pavement,  399 
Anura,  256,  257 
Aphididae,  437 
Aphids,  437 
Aphis,  *4io 

grain,  496 

green,  439 

peach,  442 
Si? 


5*8 


INDEX 


Aphis,  rosy,  439,  *44o 
woolly,  440,  *44i 

Aphis  brassicce,  482 
A.  forbcsi,  473 
A.  maidi-radicis,  492 
A.  persiccE-nigcr,  442 
A.  pomi,  439 
A.  sorbi,  439,  *44o 

Apis  mellifica,  *i2y,  334 

Apple-maggot,  425 

Apple-tree  borer,  436 

Apoda,  256 

Aptera,  154 

Apteryx,  274 

Archiannelida,  98 

Arachnida,  206 

Araneina,  206 

Argas  persicus,  212,  *3S6 

Argentinidae,  252 

Argonaut,  235 

Argon auta  argo,  235 

Argyrosomus,  252 

Ariolimax  californica,  *2$i 

Armadillos,  301 

Army-worms,  484,  *485 

Arrow-worms,  86 

Artemia,  113 

Arthrogastra,  206 

Arthropoda,  106 

Artiodactyla,  303 

Ascaris  canis,  81 

A.  lumbricoides ,  So 
A.  megalocephala,  80 

Ascidians,  237,  *238 

Aspidiotus  perniciosus,  445, 

Asterias  sp.  *go 

Asteroidea,  94 

Atropidae,  161 

Alropos  sp.  *i6i 

A.  divinatotia,  161 

Aulacaspis  rosae,  *468 

Aves,  273 

Axolotl,  257 


Babesia,  362 

B.  bigeminum,  363 
Baboons,  319 
Bacillus  pestis,  375 
Badgers,  315 
Balaenidae,  302 


Balanoglossus,  237 
Banteng,  *328 
Bark-borer,  injury,  514 
Bark-lice,  161 
Barnacles,  *ii5 
Barnacle-scale,  460 
Bass,  253 
Bats,  312 
Beach-fleas,  121 
Bean-weevil,  479 

thrips,  480 
Bears,  315 
Beavers,  310 
Bedbugs,  395,  *396 
Bee-hive,  observation,  *i95 
Bee-lice,  196 

-moth,  *i95 
Bees,  social,  184 

honey,  185 
Beet  leaf-hopper,  483 

aphis,  484 
Beetles,  169 

carpet,  *4oi 

ladybird,  *4O7 

predaceous  ground,  *4og 
Bembccia  marginata,  467 
Berries,  insects  injurious  to,  462 
Bill-bugs,  491 
Bird-lice,  161 
Birds,  classification,  278 

determining      and      studying, 
285 

development  and  life-history, 
277 

distribution     and     migration, 
288 

economics,  292 

external    parts    and    regions, 

*275 
feathers,  *274 

habits,  290,  292 

plumage,  289 

protection,  292 

and  seasons,  286 

song,  285 

structure,  273 

water  and  shore,  280 
Bison  bison,  *3O4,  *3©5 
Black-fies,  385,  *386 
Black-head,  of  turkeys,  351 
Black  scale,  452,  *453 


INDEX 


Bladder-worms,  75 
Blastophaga,  181 
Blattidiae,  162 
Blepharipeza  adusta,  *4og 
Blissus  leucopterus,  492,  *493 
Blister-mites,  213 
Blow-fly,  *388 
Blue-bottle  flies,  388 
Boa  constrictor,  272 
Bob-white,  *282,  283 
Boll-weevil,  *4g8 
Bombyx  mori,  *ijf>,  334 
Book-louse,  *i6i 
Boreus,  167 
Bos  sondaicus,  *328,  329 

B.  primigenius,  329 
Bot-flies,  389 

horse,  *389,  *39O 

sheep,  391 
Bovidae,  304 
Brachiopoda,  88 
Brachyura,  116,  120 
Braconidae,  180 
Braconidae,  cocoons,  *4og 
Branches,  53 
Braula,  196 
Brevoortia,  250 
Brittle-stars,  95 
Brown-tail  moth,  *5o9 

larva,  *5og 
Bruchus  pisorum,  478,  *479 

B.  obtectus,  479 
Bryobia  pratensis,  212,  468 
Bud- moth,  432 

Buffalo,  *304,  *3O5 
Bufo  halophilus,  *2$8 
Bufonidae,  258 
Bull,  *328 
Bumble-bee,  *i85 
Butterflies,  174 
Byturus  unicolor,  468 

Cabbage,  aphis,  482 

insects  injurious  to,  480 

maggots,  482 

-snakes,  86 
Caddis-flies,  168 
Calandra  granaria,  496 

C.  oryzcR,  496 
Calcarea,  62 
Callinectes  hastatus,  121 


Calliphora  wmitoria,  *388 

antennae,  *i3o 
Callithricidae,  318 
Callorhinus  alascanus,  *3i6 
Calosoma  sycophanta,  *4og 
Canary  birds,  333 
Cancer  magister,  121 
Candle-fish,  252 
Canidae,  313 
Canine  distemper,  366 
Canis  anthus,  325 

C.  aureus,  325 

C.  latrans,  313,  325 

C.  niger,  *324,  325 

C.  occidentalis,  313,  325 

C.  pallipes,  325 
Canker-worms,  428 
Capnodium,  450 
Capra  cegagrus,  330 

C.  falconeri,  330 

C.  jemlaica,  330 
Capronius  incequalis,  466 
Carassins  auratus,  249 
Carbon  bisulphide,  418 
Carcharias,  246 
Carcharodon  carcharias,  246 
Caribou,  303 
Carp,  248 

Carpenter-worm,  512 
Carpet-beetle,  *4oi 
Castor  canadensis,  310 
Castoridae,  306 
Caterpillar,  internal  structure,  136, 

*i37 

Cat-fishes,  248 
Catostomidae,  248 
Cats,  house,  325 
Cattle,  329 
Cattle  plague,  366 
Cavia,  308 
Cebidae,  318 
Cell,  defined,  35 

differentiation  and  specializa- 
tion, 40 

Centipede,  *i25 
Centrarchidae,  253 
Cephalopoda,  222,  233 
Ceratitis  capitata,  *426 
Ceratophyllus  fasciatus,  376 
Ceratopogon  spp.  386 
Cercopithecidae,  318 


20 


INDEX 


Cercopithecus,  *$ig 
Ceroplastcs  floridensis,  460 
C.  cirripediformis,  460 
Cervidae,  303 
Cervus  canadensis,  303 
Cestoda,  77 
Cete,  301 
Cetochilus,  114 
Cetorhinus,  239,  246 
Chastognatha,  86 
Chaatopoda,  98 
Chaff-scale,  456 
Chalcidae,  180 
Chameleons,  265 
Chelonia,  262 
Chelonia  mydas,  264 

C.  imbricata,  264 
Chelura,  121 
Chelydra  serpentina,  263 
Chenalopex  egyptiaca,  332 
Cherry  fruit-fly,  425 
Chicken-mites,  215 

tick,  212 

Chickens,  331,  332 
Chimaeras,  247 
Chimpanzee,  320 
Chinch-bug,  492,  *493 
Chionaspis  furfura,  448 
Chipmunk,  *3o6 
Chiroptera,  312 
Chitin,  127 
Chiton,  *22i 
Chordata,  237 
Chrysemmys  picta,  264 
Chrysomphalus  auranti,  *4S4 

C.  aonidum,  455 

Chrysomyia  macellaria,  *387,  388 
Chubs,  248 
Cicada,  437 

C.  septemdecim,  437 
Cigarette-beetle,  502 
Ciliata,  34 
Circulatory  system,  dragon-fly, 

*i4o 

Cirripedia,  115 
Citellus  tridecemilineatus,  311 
Citrus  fruits,  insects  affecting,  450 
Clams,  222 

geoduck,  *224 

hard,  223 

little-neck,  223 

razor,  225 


Clams,  soft,  223 

Washington,  224 
Classes,  denned,  53 
Classification,  meaning  and  basis, 

branches  and  classes,  55 

and  nomenclature,  51 

zoological,  51 
Clothes-moths,  400 
Clover  root-borer,  502 
Ciupea,  249 
Clupeidfe,  249 
Cobra,  272 
Coccidae,  443 

Coccinella  californica,  *4O7 
Coccus  hesperidum,  453 
Coccyges,  283 
Cockerel,  *33i 
Cockroaches,  162,  397 
Codfish,  253 
Codling-moth,  422,  *423 

cocoons,  *424 

larva,  *424 
Ccecilians,  256 
Ccelenterata,  63 
C  (Knur  us  cerebralis,  75 
Coleoptera,  169 
Colinus  virginianns,  *2&2 
Colorado  potato-beetle,  *476 
Columbae,  283 
Columba  lima,  283,  332 
Condylura  cristata,  311 
Conorrhinus  megistus,  354 
Conotrachelus  nenuphar,  426,  *42 
Copepoda,  114 
Copperheads,  269,  270 
Coral  Islands,  67 
Corals,  66,  *67 
Coregonus,  251 
Cormorants,  280,  333 
Corn  ear-worm,  486 

root-aphis,  492 

root- worm  (Western),  490 
(Southern),  490 

root  web  worm,  491 

stalk-borer,  491 
Corrodentia,  161 
Corvidae,  285 
Cotton  boll-worm,  499 
Cottontail,  306 
Cottony-cushion  scale,  *459 
Cougar,  313 
Coyote,  313 


INDEX 


521 


Crabs,  120 

Crambus  c  all gino  sell  its,  491 

Cr  angon  franciscorum,  118 

C.  mdgaris,  118 
Crayfish,  habits,  113 

structure,  107,  *iog,  *m 
Crickets,  producing  sounds,  163 
Crinoidea,  97 
Crocodiles,  265 
Crocodilia,  262 
Crocodilus  americanus ,  265 

C.  niloticus,  265 

Cross-pollination  of  flowers,  198 
Crotalus,  270 
Croton-bug,  *397 
Crustacea,  107 

classification,  113 
Cryptobranchus,  256 
Cryptolcemus  montrouzieri,  458 
Ctenocephalus  canis,  376 
Ctenophora,  68 
Cucumber-beetle,  *487 
Cucu maria  fron dosa,  *95 
Culex  sp.  mouthparts,  *i^6 

C.  fatigans,  384 
Currant,  aphis,  470 

saw-flies,  469 

stem-girdler,  469 
Cuttlefishes,  233 
Cut-worms,  484,  *4&5 

climbing,  432 
Cyclops,  *H4 
Cyclostomata,  239 
Cydia  pomonella,  422,  *423,  *424 
Cygnus  atratus,  333 

C.  nigricollis,  333 

C.  olor,  333 
Cyllene  robinice,  511 
Cynipidae,  181 
Cynomys  ludoviciamis,  311 
Cypridina,  114 
Cyprinidae,  248 
Cyprinus  carpio,  248 
Cypris,  114 

Damsel-flies,  158 
Dark  currant-fly,  471 
Dasyatis,  247 
Decapoda,  116 
Decapods,  235 
Deer,  303 
Delhi  boil,  354 


Delphinida;,  302 
Dendroctonus ,  515 
Dendrostomum  cronihelmi,  "103 
Dermacentor  venustus,  364 
Dermanyssus  gallince,  215 
Development,  embryonic,  45 

in  metazoa,  43 

post  embryonic,  45 
Devil-fish,  *234 
Diabrotica  longicornis,  490 

i2-punclata,  *48j,  490 

D.  mttata,  486 
Diatr&a  zeacolella,  491 
Diddphys  virginiana,  300 
Dimorphism,  65 
Dinosaurians,  261 
Dipneusti,  255 
Dipnoi,  255 
Dipodidae,  306 
Diptera,  170 
Disease  and  shell-fish,  228 

and  parasites,  349 
Dissosteira  Carolina,  *i4o 
Dobson-fly,  167 

Dog,  3.13,  324 
Dolphins,  302 
Donkeys,  327 
Doris  tuberadata,  *233 
Dourine,  355 
Doves,  283 
Dragon-flies,  *is8 

nymph,  *i59 
Duck-bill,  300 
Ducks,  280 

domestic,  332 
Dugongs,  301 
Dysentery,  amoebic,  350 
Dyticus  sp.  *i(x) 

Eagles,  283 

Ear-shells,  232 

Earthworm,  cross  section,  *io2 

habits,  98 

dissection,  *ioo 

structure,  99 
Earwigs,  164 
Echidna,  300 
Echinodermata,  89 
Echinodoris  sp.  *233 
Echinoidea,  95 
Echinorhynelus  gigas,  87 
Ecology,  346 


522 


INDEX 


Ectobia  germanica,  *$w 
Eels,  249 
Eel- worms,  80 
Egg,  fertilization,  46 
Elaphidion  villas  um,  513 
Elaps  fttlvius,  270 
Elasmobranchii,  245 
Electric-rays,  247 
Elephant-fishes,  247 
Elephantiasis,  84 
Elk,  303 
Elm,  aphis,  *5i2 

leaf-beetles,  511 
Embiotocidae,  253 
Embryology,  45 
Embryonic  development,  45 
Emulsion,  kerosene,  416 

distillate  oil,  416 

carbolic  acid,  417 
Endentata,  300 
Engraulidae,  250 
Entero-hepatitis,  351 
Entomostraca,  113 
Eohippus,  325 
Ephemeridae,  156 
Ephestia  kuehnietta,  497 
Epitrix  sp.  477 

E.  parvida,  501 
Epochra  canadensis,  470,  *47i 
Equus,  326 

E.  caballus  fossilis,  325 

E.  onager,  327 

E.  przewalski,  325 

E.  tceniopus,  327 
Erethizon  dorsatus,  308 

E.  epixanthus,  308 
Erethizontidae,  306 
Eriophyes,  213 

E.  pyri,  434 
Ermine,  314 
Esocidae,  252 
Euglena,  34 
Eulachon,  252 
Eumetopias  stelleri,  318 
Euplexoptera,  164 
Euproctis  chrysorrhcea,  *5O9 
European  fruit-Lecanium,  448 
Eutettix  tenetta,  483 
Euthrips  pyri,  433 
Evolution,  335 

factors,  336 

proof,  344 


Eyes,  compound,  130 
facets,  *i32 

longitudinal  section,  *i3i 
simple,  132 


Fasciola  hepalica,  70,  *7i 

F.  magna,  72 
Families,  defined,  52 
Feather-stars,  97 
Felidae,  312 
Felis  concolor,  313 

F .  maniculata,  325 

F.  pardalis,  313 

F.  onca,  313 
Feridae,  312 
Fertilization  of  egg,  46 
Fiber  zibethictis,  309 
Fidia  mticida,  465 
Field    and    forage    crops,    insects 

affecting,  489 
Fig- wasp,  181 
Filaria  bancrofti,  84 

F.  loa,  86 

F.  medinensis,  86 
Filaria  in  mosquito,  *384 
Fish  culture,  242 
Fishes,  239,  247 

epidemics  among,  365 
Flat-worms,  69 

classification,  77 
Flea-beetles,  477 
Flea,  172 

cat  and  dog,  173,  376 

human,  *i73,  *376 

plague,  375,  376 

rat,  376 
Flesh-flies,  388 
Flies,  two- winged,  170 
Flounder,  253,  *254 
Foraminifera,  33 
Forest    and    shade    trees,    insects 

affecting,  506 
Foxes,  313 
Fringe- wings,  166 
Fringilla  canariensis ,  333 
Fringillidae,  285 
Frog,  *4,  257 

external  structure,  5 

internal  structure,  6 

life-history  and  habits,  12 

skeleton,  *n 


INDEX 


523 


Gadidae,  253 

Galerucella  htteola,  511 

Galleria  mellonella,  *iQ5 

Galley- worm,  124 

Gall-flies,  181 

Gallinae,  282 

Callus  bankiva,  *332 

Garden  truck,  insects  affecting,  475 

Gar-pikes,  248 

Gastrophilus  equi,  *^8g 

larvae,  *3go 
Gastropoda,  222 
Gastropods,  marine,  231 
Gavial,  265 

Gavialis  gangeticus,  265 
Geese,  280 

domestic,  332 
Genus,  denned,  51 
Geomyid<z,  306 
Gephyrea,  98 
Gibbons,  319 
Gid,  75 

Gila  monster,  *266 
Gipsy  moth,  *507 

larva,  *5o8 
Glires,  305 
Glossina  morsitans,  353 

G.  palpalis,  353 
Glover's  scale,  456 
Glugea  bombycis,  364 
Glycimeris  generosa,  *224 
Goat,  Rocky  Mountain,  304,  330 
Goldfish,  249,  333 
Gonionema  vertens,  *65 
Gophers,  308 
Gorilla,  320 
Gorilla  gorilla,  320 
Grain  aphis,  496 

beetle,  saw-toothed,  *497 

moth,  Angumois,  497 

weevil,  496 
Grantia,  58 
Grape  curculio,  466 

-berry  moth,  466 

leaf-hopper,  466 

imported  root-worm,  466 

root-worm,  465 
Grape-vine,  phylloxera,  463,  *464 

flea-beetles,  466 
Grasshoppers,  control,  504 

external  structure,  14,  *i8 

immature  stages,  *i4 


Grasshoppers,  internal  anatomy,  18 
mouth-parts,  *i44 
producing  sounds,  163 

Grayling,  252 

Green-fruit  worms,  *432 

Gribbles,  122 

Ground-hog,  310 

Grubs,  503 

Guinea-pigs,  308 

Guinea-worm,  86 

Gulls,  280 

Gulo  luscus,  314 

Gymnonychus  appendiculatus,  469 

Hwmatobia  serrata,  387 
Hcematopinus,  394 

//.  asini,  *393 
Hamonchus  contortus,  81 
Hag-fish,  239 
Hair-snakes,  86 
Halibut,  253 
Haltica  sp.  466 
Hares,  306 

Harlequin  cabbage-bug,  482 
Harvest-mites,  213 
Hawks,  283 
Heliothis  obsoleta,  486 
Heliothrips  fasciata,  480 
Hell-bender,  256 
Hellebore,  white,  415 
Hell-grammite,  167 
Heloderma,  266 

H.  suspectum,  *266 
Hemerocampa  leucostigma,  431 

//.  velusta,  *430,  *43i 
Hermit-crabs,  n8,  *iig 
Hemiptera,  164 
Hemispherical  scale,  453 
Heredity,  338 
Herodiones,  281 
Herring,  249 

lake,  252 
Hesperina,  179 
Hessianrfly,  *494 
Heterocera,  179 
Heterodon,  269 
Heteroptera,  165 
Hip  pa,  1 20 
Hirudinea,  98 
11  ir iido  medicinalis,  *io4 
Hirundinidae,  285 


524 


INDEX 


Histogenesis,  152 
Histolysis,  152 
Hogs,  327 
Holocephali,  247 
Holothuroidea,  96 
Homarus  americanus,  117 

H.  grammaris,  117 
Hominidas,  320 
Homoptera,  165 
Homo  sapiens,  320 
Honey-bee,  184,  185.  *i86,*334, 

antenna,   *i3o 

external  structure,  *i27 

legs,  *i33 

mouth-parts,  *i2Q 

queen,  drone,  worker,  *i86 

reproductive  organs,  143 

ventral  view  of  worker,  *i9i 
Hookworm,  *82 

disease,  81 

Old  World,  *83 
Horned  toad,  267 
Horn-flies,  387 
Horn-worms,  499 
Horse-fly,  *i7i,  *386 
Horses,  325,  *327 

four-toed,  326 
House-fly,  and  disease,  377,  *3?8 

foot,  *38o 

head,  '379 

larvae  and  pupa?,  *38i 

mouth-parts,  *i47 
Hydra,  longitudinal  section,  *23 

structure  and  habits,  21,  *22 
Hydrocyanic  acid  gas,  418 
Hydrodamalis  gigas,  301 
Hydroids,  64 
Hydrozoa,  64 
Hyla  versicolor,  258 
Hylastinus  obscurus,  502 
Hylidas,  258 
Hymenoptera,  179 
Hypoderma  lineata,  *39O 

larvae,  *39i 

H.  bovis,  390 

Icerya  purchasi,  407,  *4o8,  *459 

Ichneumon-fly,  *i8i 

Ichneumonidae,  180 

Icthyosaurians,  261 

Iguanas,  267 

Imported  grape  root-worm,  466 


Imported  cabbage-worm,  480,  *48i 

current-borer,  *^6g 
Infantile  paralysis,  366 
Infusoria,  34 
Insecta,  125 
Insecticides,  413 
Insectivora,  311 
Insects,  125 

antennae,  129,  *i3o 

classification,  153 

controlling,  403 

natural  enemies,  405 

parasites,  407,  408 

predaceous,  407 

senses,  129 
Ipidae,5i5 

I  PS,  5i5 

Iridomyrmex  humilis,  398,  *399 
Ischnochiton  magdalenensis,  *22i 
Isolation,  343 

Isopod,   *I2I 

Isopoda,  121 
Isoptera,  159 
Isosoma  tritici,  495 
I.  grandi,  495 
Itch-mite,  *2i4 
Ixodes  ricinns,  *2io 
Jaguar,  313 
Janus  integer,  469 
Jelly-fishes,  64,  *6$ 
Jew-fish,  253 
Jiggers,  213 

JtlluS  Sp.,   *I24 

Kangaroo,  300 

Katydids  producing  sounds,  163 
Kiwi,  274 

Ladybird-beetle,  *4O7 
Lake-flies,  156 
Lamellibranchia,  221 
Lampreys,  239 
Lampropcltis  boyli,  *26g 
Lamp-shells,  88 
Lancelet,  238 
Lasioderma  serricorne,  502 
Lasiurus  borealis,  312 
Lasius  brunneus,  492 
Latax  kttris,  314 
Laterodectus  mactans,  207 
Lead,  arsenate,  415 
Lecanium  corni,  *448 
Leeches,  104 


INDEX 


525 


Lcishmannia  donovani,  354 
Lemuroidea,  318 
Lemurs,  318 
Leopard-moth,  513 
Lepas  hiUi,  *ii5 
Lepidoptera,  174 
Lepidosaphes  becki,  455 

L.  gloveri,  456 

L.  ulmi,  447 
Lepisma  sp.  *i55 

L.  domestica,  156 

L.  saccharina,  155 
Lepisosteidae,  248 
Leporidae,  306 
Leptinotarsa  decemlineata,  * 
Leptocardii,  238 
Leptocephalidae,  249 
Lepus  texanus,  307 

L.  syfaaticus ,  306 
Leucandra  apicalis,  *sg 
Leucania  unipuncla,  *48s 
Lice,  392 

bird,  395 
Life  processes,  42 
Ligyrus  gibbosus,  antennae,  * 
Limicolae,  281 
Limnoria,  122 
Limulus,  121 
Lions,  312 

Lipeurus  baculus,  *i62 
Lithobians,  124 
Liver-flukes,  70,  *ji 
Lizards,  *266 
Lobster,  116 
Locust-borer,  511 
Loligo  opalescens,  *235 
Longipennis,  280 
Louse,  body,  *392 

chicken,  *394 

crab,  394 

head,  393 

horse,  *393 
Lucilia,  388 
Lumbricus  sp.,  *ioo 
Luna-moth,  *i78 
Lung-fishes,  255 
Lutra  canadensis,  314 
Lutreola,  314 
Lynx,  313 
Lynx  canadensis,  313 

L.  rufus,  313 
Lysiphlebus  testaceipes,  496 


Machera  palula,  225 
Mackerel,  252 
Macrochelys  lacertina,  263 
Macrochires,  283 
M acrodactylus  sttbspinosits,  466 
Macrosiphum  pisi,  480 
Macrura,  116 

M alacoclemmys  palustrus,  264 
Malacosoma  americana,  427,  *429 
'  Malacostraca,  116 
Mai  du  coil,  355 
Malarial  mosquito,  *36o 

parasite,  *358 
Mai  de  coder  as,  355 
Mallophaga,  161,  395 
Mammalia,  295 
Mammals,  295 

body,  form  and  structure,  295 

classification,  299 

development  and  life-history, 

AT  2" 

Man,  320 

Manatees,  301 

Mange-mite,  214 

Mantidae,  162 

Mantis,  162 

Margaropus  annnlatus,  *362 

Marine  protozoa,  32 

worms,  *io3 
Marmosets,  318 
Marmolta,  310 
Marsupialia,  300 
Mastigophora,  34 
Mayetiola  destructor,  *494 
May-fly,  *is6 
Mealy-bug,  *457,  *4s8 
Mecoptera,  167 
Medicinal  leech,  *io4 
Mediterranean  flour-moth,  497 

fruit-fly,  *426 
Medusae,  64,  *65 
Melanerpes  erythrocephalus,  *284 
Melanoplus  spretus,  164 
Melanotus  variolatus,  antenna,  *i3O 
Meleagris  gallopavo,  333 
Melittia  satyriniformis ,  487 
Melospiza  cinerea,  *28? 
Mendelian  principles,  339 
Menhaden,  250 
Menopon  pallidum.  *394,  395 
Mephitis,  314 
Mermis  albicans,  86 


526 


INDEX 


Mesohippus,  326 
Metamorphosis,  149 

complete,  150,  *i5i 

incomplete,  *i49 
Metazoa,  39 

reproduction  and  development, 

43 

Mice,  309,  310 
Microfilaria,  *8s 
Microtus,  310 
Milliped,  *i24 
Minnows,  249 
Mink,  314 
Miscible  oils,  417 
Mistichthys,  239 
Mites,  212 
Mole,  311 
Mollusca,  216 
Molluscoida,  88 
Monarch  butterfly,  metamorphosis, 

ISI 

Monkeys,  318 
Monomorium  minimum,  399 

M.  pharaonis,  398 
Monophadnoides  rubi,  468 
Monotremata,  299 
Monotremes,  299 
Moose,  303 
Mosquitoes,  control,  371 

eggs  and  larvae,  *368 

life-history  and  habits,  368 

malaria-carrying,  369 

mouth-parts,  *i46 

pupae,  *3&9 

yellow  fever,  373 
Moth,  174 

codling,  *423 

clothes,  400 

oak-tree,  *4io 

tussock,  *43o 
Mouth-parts,  different  types,  143 

grasshopper,  *i44 

honey-bee,  *i29 

house-fly,  *i47 

mosquito,  *i46 

sphinx-moth,  *i48 

water-bug,  *i4S 
Mud-eels,  256 
Mugilidae,  252 
Mullet,  252 

Multiceps  multiceps,  75,  *^6 
Murgantia  hislrionica,  482 
Muricidae,  232 


Murrina,  355 

Mitsca  domestica,  *378 

mouth-parts,  *i47 
Mus  decumanns,  309 

M.  muscnlus,  310 

M.  rattus,  309 
Muskrat,  309 
Mussels,  222 

fresh  water,  216 

and  buttons,  220 

and  pearls,  220 

sea,  *223 
Mustelidae,  314 
Mustelus,  246 
Mutation,  336 
Mya  arenaria,  223,  *224 
Mycetozoa,  35 
Myotis  subulatus,  312 
Myriapoda,  123 
Myrmeleon  sp.  *i67 
Mytilus  edulis,  *22$ 
Myxosporida,  365 
Myzus  ribis,  470 

Nagana,  354 

Naja  tripudians,  272 

Natrix,  269 

Nautilus,  chambered,  236 

paper,  235 

Necator  americanus,  *82 
Necturus,  256 
Nemathelminthes,  79 

classification,  86 
Nematoda,  86 
Nematomorpha,  86 
Neotoma  pennsylvanica,  309 
Nephrops  norwegicus ,  118 
Nereis,  sp.,  103 
Neuroptera,  166 
Nicotine  solutions,  417 
Noctiluca,  34 
Non-calcarea,  62 
Notophthalmus  lorosus,  *2$7 
Notropis,  248 

Novius  cardinalis,  407,  *4o8,  460 
Nudibranchs,  *233 

Oak-tree  moth,  *4io 

pruner,  513 

twig-girdler,  *5i3 
Oberea  bimacula,  468 
Ocellus,  132 
Ocelot,  313 


INDEX 


527 


Octopods,  234 

Octopus,  233,  234 

Odobenidas,  318 

Odobenus  obesus,  318 

Odocoileus,  303 

Odonata,  158 

Oestridae,  389 

Oestrus  ovis,  391 

Oncorhynchus ,  250 

One-cell  animals,  39 

Onion-maggot,  488 

Onycophora,  123 

Ophibolus,  269 

Ophiuroidea,  95 

Opossums,  300 

Orang-utans,  319 

Orca,  303 

Orcamnos  montanus,  304 

Orchard  pests,  421 

Orders,  denned,  52 

Organs  and  functions, 

principal  systems,  43 

Ornithodorus  moubata,  212, 

Ornithorhynchus,  300 

Orohippus,  326 

Orthoptera,  162 

Ostracoda,  114 

Ostrea  angulata,  227 
O.  edulus,  227 
O.  lurida,  *226 
O.  virginiana,  225 

Ostriches,  *279,  333 

Otariidae,  316 

Otter,  314 

Oviparous,  260 

Ovis  arkal,  *S29,  33° 
0.  canadensis,  304 
O.  musimon,  330 
O.  tragelaphus,  330 

Ovoviparous,  260 

Ox  warble-fly,  *39O 
larva,  *39i 

Oysters,  225 
pearl,  228 

Oyster-shell  scale,  447 

Pagarus  sp.,  *ii9 
Paleacrita,  vernata,  429 
Palinurus.  118 
Paludicolae,  281 
Pan  troglodytes,  320 
Papaipema  nitella,  478 


Papirius  maculosus,  *i55 
Paramcecium,  structure  and  habits, 

29,  *3Q 
Parasita,  165 
Parasites,  and  disease,  349 

denned,  350 
Paris  green,  414 
Parlatoria  pergandi,  456 
Passeres,  283,  285 
Paw  cristatus,  333 
Peach-borer,  434 
Peach  twig-borer,  435 
Peacocks,  332 
Pear-leaf  blister-mite,  434 
Pearl-oysters,  228 

shell,  *229 
Pearls,  77 

and  mussels,  220 
Pear  thrips,  *433 
Pea  aphis,  480 

weevil,  478 
Pebrine,  364 
Pecten,  224 
Pediculidae,  392,  393 
Pediculus  capitis,  393 

P.  vestimenti,  *392,  393 
Pegomyia  brassicce,  482 

P.  ceparum,  488 
Pelecypoda,  221 
Pellagra,  384 
Pemphigus  beta,  484 
Pentacrinus  sp.,  *g6 
Perch,  253 
Percida?,  253 
Peripatus,  123 

P.  eiseni,  *i23 
Periplaneta  americana,  397 

P.  auslralasia,  397 

P.  orientalis,  397 
Perissodactyla,  303 
Petromyzon,  239 

P.  marinus,  *2^g 
Pheasants,  282,  333 
Phlososinus  cristatus,  injury,  *5i4 
Phlebotomus  pappataci,  385 
Phlegethontius  quinquemacidata, 

*5°° 

P.  sextata,  500 
Phoca  mtulina,  315 

P.  grwnlandica,  316 
Phocidae,  315 
Phoebe,  *4o6 


528 


INDEX 


Phryganidia  californica,  *4io 

Phrynosoma,  267 

Phthorimcea  operculella,  478,  501 

Phyllopoda,  113 

Phylloxera  vastatrix,  463,  *464 

Physeteridae,  302 

Phytonomus  murinus,  502,  *5O3 

Pici,  283 

Pickerel,  252 

Pigeons,  283 

domestic,  331 

passenger,  283 
Pike,  252 

wall-eyed,  253 
Pimpla  conquisitor,  *i8i 
Pinnipedia,  315 
Piroplasma,  362 
Pisces,  239 
Plague  and  fleas,  375 
Planarians,  69 
Planaria,  sp.,  *7o 
Plant-lice,  437 
Planula,  64 
Plasmodium,  357 

P.  falciparum,  359 

P.  malarial,  359 

P.  vivax,  359 

Plathemis  trimaculata,  *i58 
Platyhelminthes,  69 
Platypus,  300 
Plecoptera,  157 
Pleuronectidae,  253 
Plum-curculios,  426,  *427 
Poliomyelitis,  366 
Polychrosis  viteana,  466 
Polymorphism,  65 
Polyna  brevisetosa,  *io3 
Polynices  lewisi,  *2$2 
Polypus,  234 

P.  apollyon,  *2$4 
Polyzoa,  88 

Pontia  rapes,  480,  *48i 
Porcupines,  308 
Porifera,  62 
Porpoises,  *3O2 
Porthetria  dispar,  *SO7 
Portugese  man-of-war,  65 
Post-embryonic  development,  45 
Potato  stalk-borer,  477 

tuber-worm,  478 
Prairie-dogs,  311 
Prawns,  118 


Primates,  318 
Prionoxystns  robinae,  512 
Pristis  peclinatus,  247 
Proboscidia,  303 
Proctotrypidae,  180 
Procyonidas,  315 
Prater os pongia,  35 
Protohippus,  326 
Protophyta,  32 
Protoplasm,  35 
Protorohippus,  326 
Protozoa,  classification,  34 

parasitic,  34 

reproduction  in,  37 
Pseudococcus  citri,  *4$8,  *4S7 
Psendopleuronectes  americann-s,*2^4 
Psittaci,  283 
Psocidae,  161 
Psoroptes  communis,  214 
Pier  onus  ribesi,  469 
Pterosauria,  260 
Plerostichus   calif ornicus ,    antenna, 

.*i30 

Pthirius  inguinalis,  394 
Publications,  Government,  419 
Pulex  irritans,  *i73,  376 
Pulicidae,  172 
Puma,  313 

Purple  scale,  455,  *456 
Putorius  erminea,  314 
Pygopodes,  280 
Pyrethrum,  418 
Python,  272 

Quail,  *282 

Rabbits,  306 

domestic,  331 
Raccoons,  315 
Radiolaria,  33 
Railroad-worm,  425 
Raja  erinacea,  *2$6,  247 

R.  Icevis,  247 
Rana  catesbiana,  257 
Rangifer  caribou,  303 
Ranidae,  257 
Raptores,  283 
Raspberry  byturus,  468 

cane-borer,  468 

root-borer,  467 

saw-fly,  468 
Rasores,  282 


INDEX 


529 


Ratitas,  279 
Rats,  309 
Rattlesnakes,  269 

head,  *2fi 

rattles,  *2jo 
Rays,  247 

Red-necked  cane-borers,  468 
Red  scale,  *454 
Red  spider,  212 
Reindeer,  303 
Relapsing  fever,  356 

tick,  *3S6 
Repellents,  419 
Reptilia,  260 
Resin  spray,  417 
Rhagoletis  cingu-lata,  425 

R.  pomenella,  425 

R.  ribicola,  471 
Rhizopoda,  34 
Rhiptoglossi,  265 
Rhopalocera,  178 
Rhynchocephalia,  262 
Rice- weevil,  496 
Rocky  Mountain  fever,  364 
Rodents,  305 
Rosalina  varians,  *33 
Rose-chafer,  466 
Rose  scale,  *468 
Rotifers,  *87 

Sacculina,  116 

Saissetia  hemisphcerica,  453 

S.  olece,  452,  *453 
Salamander,  *257 
Salmo  irideus,  *  251 

S.  salar,  251 
Salmon,  250 
Salmonidae,  250 
Salvelinus,  251 
Sand-bugs,  120 
San  Jose  scale,  445,  *446 
Sanninoidea  exitiosa,  434 

S.  opalescens,  *434,  *43S 
Saperda  Candida,  436 
Sapphirina,  114 
Sap-suckers,  285 
Sarcophaga,  388 
Sar copies  scabiei,  213,  *2i4 
Sardinella,  249 
Sardines,  249 
Sauria,  265 
Saw-fish,  247 


Saw-flies,  180 
Saxidomus  nuttatti,  224 
Scab-mite,  214 
Scale  insects,  443 
Scalops  aquaticus,  311 
Scaphopoda,  222 
Sceloporus  occidentalis,  *266 
Schistocerca  americana,  "163 
Schizoneura  lanigera,  440,  *44i 

S.  nlmi,  *si2 
Schizothoerus  nuttalli,  224 
Sciuridas,  306 
Sciuropterus  volans,  310 
Sciurus  carolinensis ,  310 

5.  hudsonicus,  310 

S.  litdovicianus,  310 

S.  niger,  310 
Scolopendra,  124,  *i2S 
Scolyius,  515 
Scombridae,  252 
Scorpion-flies,  167 
Scorpions,  206 
Screw-worm  fly,  *387,  388 
Scurfy-scale,  448 
Scutellisla  cyanea,  452 
Scutigera  forceps,  124 
Scyphozoa,  66 
Sea-anemones,  *63,  66 

cows,  301 

cucumbers,  *95,  96 

lily,  *96,  97 

mats,  88 

slugs,  233 

squirts,  237,  *238 

urchin,  *94,  95 
Sea-lions,  316,  318 
Seals,  315 

fur,  *3i6 
Segregation,  343 
Selection,  artificial,  321,  342 

natural,  342 
Serpentes,  265 
Serphus  dilatatus,  "165 

mouth-parts,  "145 
Serranidae.  253 
Sesia  rutilans,  *4?2,  473 
Sex,  46 
Shad,  249 
Sharks,  245 
Sheep,  *330 

Rocky  Mountain,  304 

wild,  *329 


53° 


INDEX 


Shell- fish  and  disease,  228 

Ship-worms,  229 

Shrews,  311 

Shrimps,  118 

Sialidae,  167 

Silk- worm,  *ij6,  334 

diseases,  364 

Silpha  ramosa,  antenna,  *i3o 
Siluridae,  248 

Silvanus  surinamensis ,  *4Q7 
Silver-fish,  155,  156 
Simiidae,  319 
Simulidae,  385 
Simulium,  *386 
Siphonaptera,  172 
Siren,  256 
Sirenia,  301 

Sitotroga  cerealella ,  497 
Skates,  *246,  247 
Skunk-bear,  314 
Skunks,  314 
Sleeping  sickness,  352 
Slime  moulds,  35 
Slime  slugs,  123 
Sloths,  300 
Slugs,  231 
Smelt,  252 

Smynthurus  hortensis,  155 
Snails,  230 

Snake-bites,  treatment,  271 
Snakes,  267 

coral,  270 

garter,  *268 

king,  *26g 

water,  269 
Snow-flea,  167 
Soft  brown-scale,  453 
Sow-bug,  *i2i 
Sparrow,  *287 
Species,  defined,  51 
Spermophiles,  310,  311 
Sphargis  coriacea,  264 
Sphecina,  183 
Spenophorus  sp.,  491 
Sphinx-moth,  mouth-parts,  "148 
Spiders,  206 

hour-glass,  207 
Spilogale,  314 
Spirochceta,  356 

S.  duttoni,  357 

S.  marchouxi,  357 

5.  novyi,  357 


Spirochceta  pallidula,  357 

S.  recurrentis,  357 
Spirochaetae,  34 
Spirochaetes,  355 
Spirochaetosis,  357 
Sponges,  bath,  *6i 

boring,  62 

classified,  62 

structure,  58 

vase-shaped,  *59 
Spontaneous  generation,  36 
Sporozoa,  34,  357 
Spotted  fever,  364 
Spring-tail,  *iss 
Sqstabu,  246 
Squamata,  262 
Squash-vine  borer,  487 

bug,  487 

Squids,  233,  *23S 
Squirrels,  310 
Stable-fly,  *366,  382,  *383 
Star-fish,     cross     section     of    ray, 

*92 

dissection,  *go 

structure,  89 
Steganopodes,  280 
Stegomyia  fasciala,  373,  *374 
Sting-rays,  247 
Stomach- worm,  81 
Stomoxys    calcitrans ,     *365,     *383, 

.387 

Stone-flies,  *i57 
Strawberry  crown-borer,  472 

crown-moth,  473 

root-louse,  473 

root- worms,  473 

weevil,  473 

Striped  cucumber-beetle,  486 
Strongylocentrotus  franciscaniis,  *94 
Strnthio  camelus,  279,  333 
Sturgeons,  247 
Suckers,  248 
Sulphur-lime,  415 
Sunfishes,  253 
Surf-fish,  253 
Surra,  354 
Sus  scrofa,  327 

5.  viftatus,  329 
Swamp  fever,  366 
Swans,  280,  333 
Sympetrum  illoliim,  *i59 
Syphilis,  357 


INDEX 


53i 


Tabanidae,  387 

Tabanus  punctifer,  *iyi,  *386 
Tachina-fly,  408,  *4og 
Tcenia  saginala,  *74,  *75 

T.  solium,  73 
Tapes  staminea,  224 
Tape-worms,  73,  *74 
Tarantulas,  208 
Tatu  novemcinctum,  301 
Taxidea,  315 
Teleostomi,  247 
Tent-caterpillars,  427,  *42g,  511 

tent,  *428,  *SIQ 
Tenthredinidae,  180 
Teredo,  229 
Termes  flavipes,  160 
Termites,  159,  *i6o 
Termopsis  augusticollis,  161 
Terrapins,  263 
Testudo,  *263,  264 
Telramorium  caspilum,  399 
Tetranychus  bimaculatus,  212 

T.  mytilas pidis ,  213 

T.  sexmaculatus ,  213 
Texas  fever,  362 

tick,  *362 

Thais  lamellosa,  *2$2 
Thalcectos  maritimus,  315 
Thamnophis,  269 

T.  parietalis,  *268 
Theobaldia    incidens,    eggs,    larvae, 
*368 

female,  *37o 

male,  *37i,  *372 

pupae,  *369 

Thorn-headed  worms,  87 
Thread-worm,  80 
Thrips,  1 66 
Thymallidae,  252 
Thysanoptera,  166 
Thysanura,  155 
Ticks,  209 

castor-bean,  *2io 

disease-carrying,  *3S6,  *362 

fowl,  *356 

relapsing  fever,  *356 
Tiger,  312 

Tinea  pellionella,  *4OO 
Tmetocera  ocellana,  432 
Toad,  *2S8 
Tobacco  flea-beetle,  501 

extracts,  417 


Tobacco  leaf-miner,  501 

-worms,  499,  *5<x> 
Tortoise,  262,  *263 
Toxoptera  graminum,  496 
Tree-frogs,  258 
Trematoda,  77 
Treponema  pallidum,  357 
Trichechus  latirostris ,  301 
Trichina,  79,  *8o 
Trichinella  spiralis,  79 
Trichobaris  trinotata,  477 
Trichoptera,  168 
Trionyx,  263 
Triopha  modesta,  *233 
Trochelminthes,  87 
Tropasa  luna,  *ij8 
Trout,  251 
Trypanosoma  brucei,  354 

T.  cruzi,  354 

T.  equinum,  355 

T.  equiperdum,  355 

T.  evansi,  355 

T.  gambiense,  *352 

T.  hippicum,  355 

T.  lewisi,  352 
Trypanosomes,  352 
Tsetse-fly,  *353 

disease,  354 
Turbellaria,  77 
Turdidae,  285 
Turkey,  333 
Turtles,  262,  263 
Tussock-moth,  *43O,  *43i,  511 

white-marked,  431 
Tyloderma  fragarice,  472 
Typhlocyba  comes,  466 

T.  mdnerata,  *4-6f 
Typhoid  and  flies,  380 
Tyrannidae,  285 

Uca  spp.,  121 

Uncinararia  duodenalis,  84 

Uncinariasis,  81 

Ungulata,  303 

Unionicola,  220 

Urochorda,  237 

Urodela,  256 

Urosalpinx,  232 

Ursidae,  315 

Ursus  americanus,  315 
U.  horribilis,  315 
U.  middendorffi,  315 


532 


INDEX 


Variation,  336 

Ventral  nerve  cord,  locust,  *i4o 
Venus  mercenaria,  223 
Vertebrates,  denned,  237 
Vespa  sp.,  *i84 
Vespina,  183 
Vinegar  eel,  *79 

Vineyards,  insects  injurious  to,  462 
Vision,  mosaic,  131 
Volvocinas,  40 
Vol-vox,  35 

Vorticella,  structure  and  habits,  *3i 
Vulpes  fulvus,  314 
V.  lagopus,  314 

Walrus,  318 
Wapiti,  303 
Wasps,  183 

digger,  "183 

Water  bug,  mouth-parts,*  145 
Water-dog,  256 

moccasin,  269 

tiger,  *i6g 
Wax-scale,  460 
Weasel,  314 
Web-worm,  484 
Whale-oil  soap,  417 
Whales,  302 
Wheat,  joint-worm,  495 

straw-worm,  495 
Wheel  animalcules,  *8? 


White-ants,  159 
Whitefish,  251 
White-fly,  451 
Wire-worms,  503 
Wolf,  *324 
Wolverine,  314 
Wolves,  313 
Woodchucks,  310 
Wood-lice,  121 
Woodpecker,  *2&4 

Xenopsylla  cheopus,  376 

Xylina  antennala,  *432 

X.  grotei,  432 

Yaws,  357 

Yellow  currant-fly,  470,  *47i 

Yellow  fever,  cause,  365 
commission,  373 
and  mosquitoes,  373 
mosquito,  *374 

Yellowjacket,  *i84 

Zalopus  calif ornianus,  318 
Zamenis  constrictor,  269 
Zapodidas,  306 
Zeuzera  pyrina,  513 
Zilla  calif  arnica,  *2Of 
Zooids,  64 
Zoology,  defined,  2 


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